Create N_queen.js

closes #365'

Author: Abhinavcode13

Famous Algorithms/N_queen.js

@@ -0,0 +1,59 @@
+function solveNQueens(n) {
+  const board = new Array(n).fill().map(() => new Array(n).fill('.')); // Create an empty NxN chessboard
+  
+  const solutions = [];
+  
+  function isSafe(row, col) {
+    // Check if no other queens are in the same column
+    for (let i = 0; i < row; i++) {
+      if (board[i][col] === 'Q') {
+        return false;
+      }
+    }
+    
+    // Check upper-left diagonal
+    for (let i = row, j = col; i >= 0 && j >= 0; i--, j--) {
+      if (board[i][j] === 'Q') {
+        return false;
+      }
+    }
+    
+    // Check upper-right diagonal
+    for (let i = row, j = col; i >= 0 && j < n; i--, j++) {
+      if (board[i][j] === 'Q') {
+        return false;
+      }
+    }
+    
+    return true;
+  }
+  
+  function solve(row) {
+    if (row === n) {
+      // Found a valid solution, push a copy of the board to the solutions array
+      solutions.push(board.map(row => row.join('')));
+      return;
+    }
+    
+    for (let col = 0; col < n; col++) {
+      if (isSafe(row, col)) {
+        board[row][col] = 'Q'; // Place a queen
+        solve(row + 1); // Recursively move to the next row
+        board[row][col] = '.'; // Backtrack by removing the queen
+      }
+    }
+  }
+  
+  solve(0); // Start solving from the first row
+  
+  return solutions;
+}
+
+// Example usage:
+const n = 4; // Change this to the desired board size
+const solutions = solveNQueens(n);
+
+console.log(`Solutions for ${n}-Queens:`);
+for (const solution of solutions) {
+  console.log(solution);
+}