Create N-Queens-ii.js

02. Algorithms/07. Backtracking/Hamilton Path/N-Queens-ii.js

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+/**
+ * @param {number} n
+ * @return {number}
+ */
+var totalNQueens = function(n) {
+    let result = 0;    
+    const board = [];
+    for(let i = 0; i < n; i++) {
+        const temp = [];
+        for(let j = 0; j < n; j++) {
+            temp[j] = '.';
+        }
+        board.push(temp);
+    }
+    const colHash = new Set();
+    const posDiagonal = new Set();
+    const negDiagonal = new Set();
+
+    function backtrack(r) {
+        if(r === n) {
+            result++;
+            return;
+        }
+
+        for(let c = 0; c < n; c++) {
+            if(colHash.has(c) || posDiagonal.has(r+c) || negDiagonal.has(r-c)) continue;
+
+            colHash.add(c);
+            posDiagonal.add(r+c);
+            negDiagonal.add(r-c);
+            board[r][c] = 'Q';
+
+            backtrack(r+1);
+
+            colHash.delete(c);
+            posDiagonal.delete(r+c);
+            negDiagonal.delete(r-c);
+            board[r][c] = '.';
+        }
+    }
+
+    backtrack(0);
+    return result;
+};