Add LeetCode #52 - N-Queens II solution in C++

Leetcode/Hard/NQueensII.cpp

@@ -0,0 +1,39 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+class Solution {
+public:
+    int totalNQueens(int n) {
+        vector<bool> cols(n, false), diag1(2 * n, false), diag2(2 * n, false);
+        int count = 0;
+        backtrack(0, n, cols, diag1, diag2, count);
+        return count;
+    }
+
+private:
+    void backtrack(int row, int n, vector<bool>& cols, vector<bool>& diag1, vector<bool>& diag2, int& count) {
+        if (row == n) {
+            count++;
+            return;
+        }
+        for (int col = 0; col < n; ++col) {
+            if (cols[col] || diag1[row + col] || diag2[row - col + n])
+                continue;
+            cols[col] = diag1[row + col] = diag2[row - col + n] = true;
+            backtrack(row + 1, n, cols, diag1, diag2, count);
+            cols[col] = diag1[row + col] = diag2[row - col + n] = false;
+        }
+    }
+};
+
+int main() {
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    Solution sol;
+    vector<int> tests = {1, 4, 8};
+    for (int n : tests) {
+        cout << "For N = " << n << ", Number of Solutions = " << sol.totalNQueens(n) << "\n";
+    }
+    return 0;
+}