From 7252e23f01c7e70d11e67f00dcc5595886b53e88 Mon Sep 17 00:00:00 2001
From: Vahagn Khachatryan <vahagn.khachatryan@gmail.com>
Date: Mon, 7 May 2018 12:11:59 +0100
Subject: [PATCH] diagonal.cpp

---
 puzzles/interviews/training/diagonal.cpp | 172 +++++++++++++++++++++++
 1 file changed, 172 insertions(+)
 create mode 100644 puzzles/interviews/training/diagonal.cpp

diff --git a/puzzles/interviews/training/diagonal.cpp b/puzzles/interviews/training/diagonal.cpp
new file mode 100644
index 0000000..5421773
--- /dev/null
+++ b/puzzles/interviews/training/diagonal.cpp
@@ -0,0 +1,172 @@
+/*
+VIM: let b:lcppflags="-std=c++14 -O2 -pthread -I."
+VIM: let b:wcppflags="/O2 /EHsc /DWIN32"
+VIM-: let b:cppflags=g:Iboost.g:Itbb
+VIM-: let b:ldflags=g:Lboost.g:Ltbb
+VIM-: let b:ldlibpath=g:Bboost.g:Btbb
+VIM-: let b:argv=""
+*/
+#include <iostream>
+#include <exception>
+#include <chrono>
+#include <algorithm>
+#include <vector>
+
+/*
+ * Give a N*N square matrix, return an array of its anti-diagonals. Look at the
+ * example for more details.
+ *
+ * Example:
+ * Input:
+ * 1 2 3
+ * 4 5 6
+ * 7 8 9
+ *
+ * Return the following :
+ * [ 
+ * [1],
+ * [2, 4],
+ * [3, 5, 7],
+ * [6, 8],
+ * [9]
+ * ]
+ *
+ * Input : 
+ * 1 2
+ * 3 4
+ *
+ * Return the following  : 
+ * [
+ * [1],
+ * [2, 3],
+ * [4]
+ * ]
+ */
+
+std::vector<std::vector<int> > diagonal(const std::vector<std::vector<int> > &A)
+{
+    size_t m = A.size();
+    size_t n = A.front().size();
+
+    std::vector<std::vector<int> > v(n+m-1);
+
+    int step = 0;
+    size_t k = 0;
+    for ( size_t i = 0; i < m; ++i, ++k ){
+        size_t c = std::min(i+1, n);
+        v[k].resize(c);
+        for ( size_t j = 0; j < c; ++j){
+            v[k][c-1-j] = A[i-j][j];
+        }
+    }
+
+    for ( size_t i = 1; i < n; ++i, ++k ){
+        size_t c = std::min(n-i, m);
+        v[k].resize(c);
+        for ( size_t j = 0; j < c; ++j){
+            v[k][c-1-j] = A[m-1-j][i+j];
+        }
+    }
+
+    return v;
+}
+
+std::vector<std::vector<int>> diagonal2(const std::vector<std::vector<int> > &A)
+{
+    size_t m = A.size();
+    size_t n = A.front().size();
+    size_t mn_min = std::min(n,m);
+    size_t r_count = n+m-1;
+
+    std::vector<std::vector<int>> v(n+m-1);
+
+    for ( int i = 0; i < m; ++i ){
+        for ( int j = 0; j < n; ++j ){
+            size_t r = i+j;
+
+            auto q = i;
+            if ( r >= n ) {
+                q -= r-n+1;
+            }
+
+            if ( !v[r].size() ){
+                auto rr = std::min( r_count-r, r+1);
+                v[r].resize(std::min(rr,mn_min));
+            }
+
+            v[r][q] = A[i][j];
+        }
+    }
+
+    return v;
+}
+
+void print( const std::vector<std::vector<int>>& A )
+{
+    return;
+    for ( const auto& a : A ){
+        for ( auto i : a ){
+            std::cout << i << ' ';
+        }
+        std::cout << std::endl;
+    }
+}
+
+template <typename SOLUTION>
+void test( SOLUTION s )
+{
+    print( s( {
+                { 1, 2, 3 },
+                { 4, 5, 6 },
+                { 7, 8, 9 }
+              } ) );
+    print( s( {
+                { 1,  2,  3 },
+                { 4,  5,  6 },
+                { 7,  8,  9 },
+                { 10, 11, 12 },
+                { 13, 14, 15 },
+                { 16, 17, 18 }
+              } ) );
+    print( s( {
+                {  1,  2,  3,  4,  5 },
+                {  6,  7,  8,  9, 10 },
+                { 11, 12, 13, 14, 15 }
+              } ) );
+}
+
+int main ( void )
+{try{
+    test(diagonal);
+    test(diagonal2);
+
+    auto begin = std::chrono::high_resolution_clock::now();
+
+    test(diagonal2);
+
+    auto mid = std::chrono::high_resolution_clock::now();
+
+    test(diagonal);
+
+    auto end = std::chrono::high_resolution_clock::now();
+    std::chrono::duration<double> seconds = end - begin;
+    std::chrono::duration<double> seconds1 = mid - begin;
+    std::chrono::duration<double> seconds2 = end - mid;
+    std::cout << "Time: " << seconds.count() << std::endl;
+    std::cout << "Time1: " << seconds1.count() << std::endl;
+    std::cout << "Time2: " << seconds2.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;
+}}
+