Some training puzzles.
This commit is contained in:
Vahagn Khachatryan
116
puzzles/interviews/training/max_points_on_a_line.cpp
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116
puzzles/interviews/training/max_points_on_a_line.cpp
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/*
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VIM: let b:lcppflags="-std=c++14 -O2 -pthread -I."
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VIM: let b:wcppflags="/O2 /EHsc /DWIN32"
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*/
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#include "stdafx.h"
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#include <iostream>
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#include <exception>
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#include <string>
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#include <chrono>
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#include <vector>
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#include <algorithm>
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#include <queue>
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#include <mutex>
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#include <condition_variable>
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#include <atomic>
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#include <unordered_map>
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#include <unordered_set>
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/*
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https://leetcode.com/problems/max-points-on-a-line/
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Given n points on a 2D plane, find the maximum number of points that lie on the same straight line.
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*/
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struct Point {
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int x;
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int y;
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Point() : x(0), y(0) {}
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Point(int a, int b) : x(a), y(b) {}
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};
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struct pairhash {
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std::size_t operator() (const Point& p) const {
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return std::hash<int>()(p.x) ^ std::hash<int>()(p.y);
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}
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};
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bool operator == (const Point& p1, const Point& p2) {
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return p1.x == p2.x && p1.y == p2.y;
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}
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Point ratio(int x, int y) {
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if (x == 0) {
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return Point(0, 1);
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}
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else if (y == 0) {
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return Point(1, 0);
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}
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else if ( x < 0 ) {
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x = -x;
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y = -y;
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}
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int a = std::max(abs(x), abs(y));
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int b = std::min(abs(x), abs(y));
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for (int c; (c = a % b); a = b, b = c);
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return Point(x / b, y / b);
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}
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int solve(const std::vector<Point>& v) {
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std::unordered_map<Point, int, pairhash> vv;
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for (const auto& p : v) {
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vv[p]++;
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}
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if (vv.empty()) {
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return 0;
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}
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else if (vv.size()==1) {
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return vv.begin()->second;
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}
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int max_points = 1;
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for (auto i = vv.begin(); i != vv.end(); i++) {
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std::unordered_map<Point, int, pairhash> s;
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for (auto j = std::next(i); j != vv.end(); j++) {
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const auto line = ratio(i->first.x - j->first.x, i->first.y - j->first.y);
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s[line] += j->second;
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max_points = std::max(max_points, s[line] + i->second);
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}
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}
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return max_points;
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}
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int main()
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{
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try {
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auto begin = std::chrono::high_resolution_clock::now();
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std::cout << solve({ { 1,1 },{ 2,2 },{ 3,3 } }) << std::endl;
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std::cout << solve({ { 1,1 },{ 3,2 },{ 5,3 },{ 4,1 },{ 2,3 },{ 1,4 } }) << std::endl;
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std::cout << solve({ { 2, 3 },{ 3, 3 },{ -5, 3 } }) << std::endl;
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std::cout << solve({ { 2, 2 },{ 3, 3 },{ 2, 2 },{ 3, 3 } }) << std::endl;
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std::cout << solve({ { 2, 2 },{ 2, 3 },{ 3, 2 },{ 3, 3 } }) << std::endl;
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auto end = std::chrono::high_resolution_clock::now();
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std::chrono::duration<double> seconds = end - begin;
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std::cout << "Time: " << seconds.count() << std::endl;
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return 0;
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}
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catch (const std::exception& e)
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{
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std::cerr << std::endl
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<< "std::exception(\"" << e.what() << "\")." << std::endl;
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return 2;
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}
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catch (...)
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{
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std::cerr << std::endl
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<< "unknown exception." << std::endl;
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return 1;
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}
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}
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148
puzzles/interviews/training/multithreaded_queue.cpp
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148
puzzles/interviews/training/multithreaded_queue.cpp
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@@ -0,0 +1,148 @@
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/*
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VIM: let b:lcppflags="-std=c++14 -O2 -pthread -I."
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VIM: let b:wcppflags="/O2 /EHsc /DWIN32"
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*/
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#include "stdafx.h"
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#include <iostream>
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#include <exception>
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#include <string>
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#include <chrono>
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#include <vector>
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#include <algorithm>
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#include <queue>
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#include <mutex>
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#include <condition_variable>
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#include <atomic>
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/*
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Queue.
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*/
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thread_local size_t this_tid;
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template <typename M>
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class MtQueue {
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std::queue<M> m_queue;
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std::mutex m_mutex;
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std::condition_variable m_push_cond;
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std::condition_variable m_pop_cond;
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std::atomic<bool> m_stopped;
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static const size_t max_queue = 100;
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public:
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/* Stop Queue */
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void stop() {
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std::unique_lock<std::mutex> lock(m_mutex);
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m_stopped.store(true);
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m_pop_cond.notify_all();
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m_push_cond.notify_all();
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}
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/* Blocks when */
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bool push(M m) {
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std::unique_lock<std::mutex> lock(m_mutex);
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while (m_queue.size() >= max_queue && !m_stopped.load()) {
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printf(" %lld: is full.\n", this_tid);
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m_push_cond.wait(lock);
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}
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if (m_stopped.load()) {
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return false;
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}
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m_queue.push(m);
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printf("%lld: size %lld.\n", this_tid, m_queue.size());
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m_pop_cond.notify_one();
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return true;
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}
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/* Blocks when empty.*/
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bool pop(M& m) {
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std::unique_lock<std::mutex> lock(m_mutex);
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while (m_queue.empty() && !m_stopped.load()) {
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printf(" %lld: is empty.\n", this_tid);
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m_pop_cond.wait(lock);
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}
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if (m_stopped.load()) {
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return false;
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}
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m = m_queue.front();
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m_queue.pop();
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printf("%lld: size %lld.\n", this_tid, m_queue.size());
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m_push_cond.notify_one();
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return true;
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}
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};
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void test() {
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MtQueue<int> q;
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auto push_proc = [&q](size_t tid) {
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this_tid = tid;
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int i = 0;
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while (q.push(2)) {
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if (++i % 101 == 0) {
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auto m = std::chrono::milliseconds(100);
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//printf("%lld: pusher waiting for %lldms.\n", this_tid, m.count());
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//std::this_thread::sleep_for(m);
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}
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}
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};
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auto pop_proc = [&q](size_t tid) {
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this_tid = tid;
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int m;
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while (q.pop(m)) {
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//printf("%lld: popper waiting for %dms.\n", this_tid, m);
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std::this_thread::sleep_for(std::chrono::milliseconds(m));
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}
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};
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std::vector<std::thread> v;
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v.reserve(16);
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v.emplace_back(push_proc, v.size());
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v.emplace_back(pop_proc, v.size());
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v.emplace_back(pop_proc, v.size());
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v.emplace_back(pop_proc, v.size());
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v.emplace_back(pop_proc, v.size());
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v.emplace_back(pop_proc, v.size());
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std::this_thread::sleep_for(std::chrono::milliseconds(500));
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q.stop();
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printf(" STOPPING.\n");
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for (auto& t : v) {
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t.join();
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}
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}
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int main()
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{
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try {
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auto begin = std::chrono::high_resolution_clock::now();
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while (true) {
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test();
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}
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auto end = std::chrono::high_resolution_clock::now();
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std::chrono::duration<double> seconds = end - begin;
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std::cout << "Time: " << seconds.count() << std::endl;
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return 0;
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}
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catch (const std::exception& e)
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{
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std::cerr << std::endl
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<< "std::exception(\"" << e.what() << "\")." << std::endl;
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return 2;
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}
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catch (...)
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{
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std::cerr << std::endl
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<< "unknown exception." << std::endl;
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return 1;
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}
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}
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84
puzzles/interviews/training/string_addition.cpp
Normal file
84
puzzles/interviews/training/string_addition.cpp
Normal file
@@ -0,0 +1,84 @@
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/*
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VIM: let b:lcppflags="-std=c++14 -O2 -pthread -I."
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VIM: let b:wcppflags="/O2 /EHsc /DWIN32"
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*/
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#include "stdafx.h"
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#include <iostream>
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#include <exception>
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#include <string>
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#include <chrono>
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#include <vector>
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#include <algorithm>
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#include <queue>
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#include <mutex>
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#include <condition_variable>
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#include <atomic>
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/*
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given an array representing a non-negative integer (ex: 123 represented
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as [1,2,3]), return the next integer (output: [1,2,4]).
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run through all edge cases (ex: [9,9,9,9,9,9,9,9] etc)
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*/
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int dig(char ch) {
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return ch - '0';
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}
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char chr(int dig) {
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return dig + '0';
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}
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std::string incr(std::string n) {
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int carry = 1;
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for (size_t i = n.size(); i-- > 0; ) {
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int ds = dig(n[i]) + carry;
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if (ds >= 10) {
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carry = ds / 10;
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ds %= 10;
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}
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else {
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carry = 0;
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}
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n[i] = chr(ds);
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}
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if (carry) {
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return chr(carry) + n;
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}
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else {
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return n;
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}
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}
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int main()
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{
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try {
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auto begin = std::chrono::high_resolution_clock::now();
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std::cout << incr("0") << std::endl;
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std::cout << incr("1") << std::endl;
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std::cout << incr("9") << std::endl;
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std::cout << incr("10") << std::endl;
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std::cout << incr("15") << std::endl;
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std::cout << incr("19") << std::endl;
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std::cout << incr("99") << std::endl;
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std::cout << incr("9999999") << std::endl;
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auto end = std::chrono::high_resolution_clock::now();
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std::chrono::duration<double> seconds = end - begin;
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std::cout << "Time: " << seconds.count() << std::endl;
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return 0;
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}
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catch (const std::exception& e)
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{
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std::cerr << std::endl
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<< "std::exception(\"" << e.what() << "\")." << std::endl;
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return 2;
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}
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catch (...)
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{
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std::cerr << std::endl
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<< "unknown exception." << std::endl;
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return 1;
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}
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}
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