feat: 0051.N皇后 更简洁清晰的javascript版本

problems/0051.N皇后.md

@@ -453,60 +453,66 @@ func isValid(n, row, col int, chessboard [][]string) bool {
 
 ### Javascript 
 ```Javascript
-var solveNQueens = function(n) {
-    function isValid(row, col, chessBoard, n) {
-
-        for(let i = 0; i < row; i++) {
-            if(chessBoard[i][col] === 'Q') {
-                return false
-            }
-        }
-
-        for(let i = row - 1, j = col - 1; i >= 0 && j >= 0; i--, j--) {
-            if(chessBoard[i][j] === 'Q') {
-                return false
-            }
-        }
-
-        for(let i = row - 1, j = col + 1; i >= 0 && j < n; i--, j++) {
-            if(chessBoard[i][j] === 'Q') {
-                return false
-            }
-        }
-        return true
-    }
-
-    function transformChessBoard(chessBoard) {
-        let chessBoardBack = []
-        chessBoard.forEach(row => {
-            let rowStr = ''
-            row.forEach(value => {
-                rowStr += value
-            })
-            chessBoardBack.push(rowStr)
-        })
-
-        return chessBoardBack
-    }
-
-    let result = []
-    function backtracing(row,chessBoard) {
-        if(row === n) {
-            result.push(transformChessBoard(chessBoard))
-            return
-        }
-        for(let col = 0; col < n; col++) {
-            if(isValid(row, col, chessBoard, n)) {
-                chessBoard[row][col] = 'Q'
-                backtracing(row + 1,chessBoard)
-                chessBoard[row][col] = '.'
-            }
-        }
-    }
-    let chessBoard = new Array(n).fill([]).map(() => new Array(n).fill('.'))
-    backtracing(0,chessBoard)
-    return result
-    
+/**
+ * @param {number} n
+ * @return {string[][]}
+ */
+var solveNQueens = function (n) {
+	const ans = [];
+	const path = [];
+	const matrix = new Array(n).fill(0).map(() => new Array(n).fill("."));
+	// 判断是否能相互攻击
+	const canAttack = (matrix, row, col) => {
+		let i;
+		let j;
+		// 判断正上方和正下方是否有皇后
+		for (i = 0, j = col; i < n; i++) {
+			if (matrix[i][j] === "Q") {
+				return true;
+			}
+		}
+		// 判断正左边和正右边是否有皇后
+		for (i = row, j = 0; j < n; j++) {
+			if (matrix[i][j] === "Q") {
+				return true;
+			}
+		}
+		// 判断左上方是否有皇后
+		for (i = row - 1, j = col - 1; i >= 0 && j >= 0; i--, j--) {
+			if (matrix[i][j] === "Q") {
+				return true;
+			}
+		}
+         // 判断右上方是否有皇后
+		for (i = row - 1, j = col + 1; i >= 0 && j < n; i--, j++) {
+			if (matrix[i][j] === "Q") {
+				return true;
+			}
+		}
+		return false;
+	};
+	const backtrack = (matrix, row, col) => {
+		if (path.length === matrix.length) {
+			ans.push(path.slice());
+			return;
+		}
+		for (let i = row; i < matrix.length; i++) {
+			for (let j = col; j < matrix.length; j++) {
+				// 当前位置会导致互相攻击 继续下一轮搜索
+				if (canAttack(matrix, i, j)) {
+					continue;
+				}
+				matrix[i][j] = "Q";
+				path.push(matrix[i].join(""));
+				// 另起一行搜索 同一行只能有一个皇后
+				backtrack(matrix, i + 1, 0);
+				matrix[i][j] = ".";
+				path.pop();
+			}
+		}
+	};
+	backtrack(matrix, 0, 0);
+	return ans;
 };
 ```