Merge pull request #6797 from OhmRamwala/patch-2

Create N-Queens_problem.cpp

Add Code Here/C++/Recursion/N-Queens_problem.cpp

@@ -0,0 +1,63 @@
+#include <iostream>
+#include <vector>
+
+bool IsSafe(const std::vector<int>& board, int row, int col) {
+    for (int i = 0; i < row; i++) {
+        if (board[i] == col ||           // Check for the same column
+            board[i] - i == col - row || // Check for left diagonal
+            board[i] + i == col + row)   // Check for right diagonal
+        {
+            return false;
+        }
+    }
+    return true;
+}
+
+void SolveNQueens(std::vector<std::vector<std::string>>& solutions, std::vector<int>& board, int row, int n) {
+    if (row == n) {
+        // All queens are successfully placed, add the solution
+        std::vector<std::string> solution(n, std::string(n, '.'));
+        for (int i = 0; i < n; i++) {
+            solution[i][board[i]] = 'Q';
+        }
+        solutions.push_back(solution);
+        return;
+    }
+
+    for (int col = 0; col < n; col++) {
+        if (IsSafe(board, row, col)) {
+            board[row] = col;
+            SolveNQueens(solutions, board, row + 1, n);
+            board[row] = -1; // Backtrack
+        }
+    }
+}
+
+std::vector<std::vector<std::string>> SolveNQueens(int n) {
+    std::vector<std::vector<std::string>> solutions;
+    std::vector<int> board(n, -1);
+    SolveNQueens(solutions, board, 0, n);
+    return solutions;
+}
+
+int main() {
+    int n;
+    std::cout << "Enter the value of N: ";
+    std::cin >> n;
+
+    std::vector<std::vector<std::string>> solutions = SolveNQueens(n);
+
+    if (solutions.empty()) {
+        std::cout << "No solutions found for N = " << n << std::endl;
+    } else {
+        std::cout << "Solutions for N = " << n << ":\n";
+        for (const auto& solution : solutions) {
+            for (const std::string& row : solution) {
+                std::cout << row << '\n';
+            }
+            std::cout << '\n';
+        }
+    }
+
+    return 0;
+}