117 lines
2.7 KiB
C++
117 lines
2.7 KiB
C++
/*
|
|
VIM: let b:lcppflags="-std=c++14 -O2 -pthread -I."
|
|
VIM: let b:wcppflags="/O2 /EHsc /DWIN32"
|
|
*/
|
|
#include "stdafx.h"
|
|
#include <iostream>
|
|
#include <exception>
|
|
#include <string>
|
|
#include <chrono>
|
|
#include <vector>
|
|
#include <algorithm>
|
|
#include <queue>
|
|
#include <mutex>
|
|
#include <condition_variable>
|
|
#include <atomic>
|
|
#include <unordered_map>
|
|
#include <unordered_set>
|
|
|
|
/*
|
|
https://leetcode.com/problems/max-points-on-a-line/
|
|
|
|
Given n points on a 2D plane, find the maximum number of points that lie on the same straight line.
|
|
*/
|
|
|
|
struct Point {
|
|
int x;
|
|
int y;
|
|
Point() : x(0), y(0) {}
|
|
Point(int a, int b) : x(a), y(b) {}
|
|
};
|
|
|
|
struct pairhash {
|
|
std::size_t operator() (const Point& p) const {
|
|
return std::hash<int>()(p.x) ^ std::hash<int>()(p.y);
|
|
}
|
|
};
|
|
|
|
bool operator == (const Point& p1, const Point& p2) {
|
|
return p1.x == p2.x && p1.y == p2.y;
|
|
}
|
|
|
|
Point ratio(int x, int y) {
|
|
if (x == 0) {
|
|
return Point(0, 1);
|
|
}
|
|
else if (y == 0) {
|
|
return Point(1, 0);
|
|
}
|
|
else if ( x < 0 ) {
|
|
x = -x;
|
|
y = -y;
|
|
}
|
|
|
|
int a = std::max(abs(x), abs(y));
|
|
int b = std::min(abs(x), abs(y));
|
|
for (int c; (c = a % b); a = b, b = c);
|
|
return Point(x / b, y / b);
|
|
}
|
|
|
|
int solve(const std::vector<Point>& v) {
|
|
|
|
std::unordered_map<Point, int, pairhash> vv;
|
|
for (const auto& p : v) {
|
|
vv[p]++;
|
|
}
|
|
|
|
if (vv.empty()) {
|
|
return 0;
|
|
}
|
|
else if (vv.size()==1) {
|
|
return vv.begin()->second;
|
|
}
|
|
|
|
int max_points = 1;
|
|
for (auto i = vv.begin(); i != vv.end(); i++) {
|
|
std::unordered_map<Point, int, pairhash> s;
|
|
for (auto j = std::next(i); j != vv.end(); j++) {
|
|
const auto line = ratio(i->first.x - j->first.x, i->first.y - j->first.y);
|
|
s[line] += j->second;
|
|
max_points = std::max(max_points, s[line] + i->second);
|
|
}
|
|
}
|
|
|
|
return max_points;
|
|
}
|
|
|
|
int main()
|
|
{
|
|
try {
|
|
auto begin = std::chrono::high_resolution_clock::now();
|
|
|
|
std::cout << solve({ { 1,1 },{ 2,2 },{ 3,3 } }) << std::endl;
|
|
std::cout << solve({ { 1,1 },{ 3,2 },{ 5,3 },{ 4,1 },{ 2,3 },{ 1,4 } }) << std::endl;
|
|
std::cout << solve({ { 2, 3 },{ 3, 3 },{ -5, 3 } }) << std::endl;
|
|
std::cout << solve({ { 2, 2 },{ 3, 3 },{ 2, 2 },{ 3, 3 } }) << std::endl;
|
|
std::cout << solve({ { 2, 2 },{ 2, 3 },{ 3, 2 },{ 3, 3 } }) << std::endl;
|
|
|
|
|
|
auto end = std::chrono::high_resolution_clock::now();
|
|
std::chrono::duration<double> seconds = end - begin;
|
|
std::cout << "Time: " << seconds.count() << std::endl;
|
|
return 0;
|
|
}
|
|
catch (const std::exception& e)
|
|
{
|
|
std::cerr << std::endl
|
|
<< "std::exception(\"" << e.what() << "\")." << std::endl;
|
|
return 2;
|
|
}
|
|
catch (...)
|
|
{
|
|
std::cerr << std::endl
|
|
<< "unknown exception." << std::endl;
|
|
return 1;
|
|
}
|
|
}
|