nQueen.java

nQueen.java

@@ -0,0 +1,69 @@
+public class NQueenProblem {
+    final int N = 4;
+    void printSolution(int board[][])
+    {
+        for (int i = 0; i < N; i++) {
+            for (int j = 0; j < N; j++)
+                System.out.print(" " + board[i][j]
+                                 + " ");
+            System.out.println();
+        }
+    }   
+    boolean isSafe(int board[][], int row, int col)
+    {
+        int i, j;  
+        for (i = 0; i < col; i++)
+            if (board[row][i] == 1)
+                return false;  
+        for (i = row, j = col; i >= 0 && j >= 0; i--, j--)
+            if (board[i][j] == 1)
+                return false;        
+        for (i = row, j = col; j >= 0 && i < N; i++, j--)
+            if (board[i][j] == 1)
+                return false;
+        return true;
+    } 
+    boolean solveNQUtil(int board[][], int col)
+    {     
+        if (col >= N)
+            return true;    
+        for (int i = 0; i < N; i++) {
+
+            if (isSafe(board, i, col)) {
+
+                board[i][col] = 1;
+
+
+                if (solveNQUtil(board, col + 1) == true)
+                    return true;
+
+
+                board[i][col] = 0; // BACKTRACK
+            }
+        }
+
+        return false;
+    }
+
+    boolean solveNQ()
+    {
+        int board[][] = { { 0, 0, 0, 0 },
+                          { 0, 0, 0, 0 },
+                          { 0, 0, 0, 0 },
+                          { 0, 0, 0, 0 } };
+
+        if (solveNQUtil(board, 0) == false) {
+            System.out.print("Solution does not exist");
+            return false;
+        }
+
+        printSolution(board);
+        return true;
+    }
+
+    public static void main(String args[])
+    {
+        NQueenProblem Queen = new NQueenProblem();
+        Queen.solveNQ();
+    }
+}