Day 17 implementation in c++ (#165)

Author: dhruv-gupta14

day17/C++/Day17.cpp

@@ -0,0 +1,62 @@
+/*
+* @author : dhruv-gupta14
+* @date : 12/01/2019
+*/
+
+#include<iostream>
+using namespace std;
+#define N 8
+
+void printBoard(int board[N][N]) {
+   for (int i = 0; i < N; i++) {
+      for (int j = 0; j < N; j++)
+         cout << board[i][j] << " ";
+      cout << endl;
+   }
+}
+
+bool isValid(int board[N][N], int row, int col) {
+   for (int i = 0; i < col; i++)    //check whether there is queen in the left or not
+      if (board[row][i])
+         return false;
+   for (int i=row, j=col; i>=0 && j>=0; i--, j--)
+      if (board[i][j])       //check whether there is queen in the left upper diagonal or not
+         return false;
+   for (int i=row, j=col; j>=0 && i<N; i++, j--)
+      if (board[i][j])      //check whether there is queen in the left lower diagonal or not
+         return false;
+   return true;
+}
+
+bool solveNQueen(int board[N][N], int col) {
+   if (col >= N)           //when N queens are placed successfully
+      return true;
+   for (int i = 0; i < N; i++) {     //for each row, check placing of queen is possible or not
+      if (isValid(board, i, col) ) {
+         board[i][col] = 1;      //if validate, place the queen at place (i, col)
+         if ( solveNQueen(board, col + 1))    //Go for the other columns recursively
+            return true;
+                   
+         board[i][col] = 0;        //When no place is vacant remove that queen
+      }
+   }
+   return false;      
+}
+
+bool checkSolution() {
+   int board[N][N];
+   for(int i = 0; i<N; i++)
+      for(int j = 0; j<N; j++)
+         board[i][j] = 0;      
+               
+   if ( solveNQueen(board, 0) == false ) {    
+      cout << "Solution does not exist";
+      return false;
+   }
+   printBoard(board);
+   return true;
+}
+
+int main() {
+   checkSolution();
+}

day17/README.md

@@ -139,4 +139,73 @@ function printBoard (chessBoard) {
 }
 
 nqueens (8);
-```
+```
+
+## C++ Implementation
+
+### [Solution 1](./C++/Day17.cpp)
+
+```cpp
+/*
+* @author : dhruv-gupta14
+* @date : 12/01/2019
+*/
+
+#include<iostream>
+using namespace std;
+#define N 8
+
+void printBoard(int board[N][N]) {
+   for (int i = 0; i < N; i++) {
+      for (int j = 0; j < N; j++)
+         cout << board[i][j] << " ";
+      cout << endl;
+   }
+}
+
+bool isValid(int board[N][N], int row, int col) {
+   for (int i = 0; i < col; i++)    //check whether there is queen in the left or not
+      if (board[row][i])
+         return false;
+   for (int i=row, j=col; i>=0 && j>=0; i--, j--)
+      if (board[i][j])       //check whether there is queen in the left upper diagonal or not
+         return false;
+   for (int i=row, j=col; j>=0 && i<N; i++, j--)
+      if (board[i][j])      //check whether there is queen in the left lower diagonal or not
+         return false;
+   return true;
+}
+
+bool solveNQueen(int board[N][N], int col) {
+   if (col >= N)           //when N queens are placed successfully
+      return true;
+   for (int i = 0; i < N; i++) {     //for each row,check placing of queen is possible or not
+      if (isValid(board, i, col) ) {
+         board[i][col] = 1;      //if validate, place the queen at place (i, col)
+         if ( solveNQueen(board, col + 1))    //Go for the other columns recursively
+            return true;
+                   
+         board[i][col] = 0;        //When no place is vacant remove that queen
+      }
+   }
+   return false;
+}
+
+bool checkSolution() {
+   int board[N][N];
+   for(int i = 0; i<N; i++)
+      for(int j = 0; j<N; j++)
+         board[i][j] = 0;      
+               
+   if ( solveNQueen(board, 0) == false ) {
+      cout << "Solution does not exist";
+      return false;
+   }
+   printBoard(board);
+   return true;
+}
+
+int main() {
+   checkSolution();
+}
+```