JavaScript算法系列--leetcode螺旋矩陣Ⅱ

給定一個正整數 n，生成一個包含 1 到 n2 所有元素，且元素按順時針順序螺旋排列的正方形矩陣。

示例:

輸入: 3
輸出:
[
 [ 1, 2, 3 ],
 [ 8, 9, 4 ],
 [ 7, 6, 5 ]
]

解法如下：

  /**
   * @param {number} n
   * @return {number[][]}
   */
  var generateMatrix = function(n) {
    if (!n) return []
    const res = []
    for (let i = 0; i < n; i++) {
      res[i] = []
      for (let j = 0; j < n; j++) {
        res[i][j] = 0
      }
    }
    // 向左前進：'left'，向右前進：'right'，向上前進：'top', 向下前進：'down'
    let direction = 'right'
    let x = 0, y = 0
    const visitedArr = []
    const col = n
    const row = n
    for (let i = 0; i < row; i++) {
      visitedArr[i] = []
      for (let j = 0; j < col; j++) {
        visitedArr[i][j] = false
      }
    }
    for (let index = 1; index <= n ** 2;) {
      switch (direction) {
        case 'right':
          for (let k = x; k < col; k++) {
            if (!visitedArr[y][k]) {
              res[y][k] = index++
              visitedArr[y][k] = true
              x = k
              if (x === col - 1) direction = 'down'
            } else {
              direction = 'down'
            }
          }
          break;
        case 'down':
          for (let k = y + 1; k < row; k++) {
            if (!visitedArr[k][x]) {
              res[k][x] = index++
              visitedArr[k][x] = true
              y = k
              if (y === row - 1) direction = 'left'
            } else {
              direction = 'left'
            }
          }
          break;
        case 'left':
          for (let k = x - 1; k >= 0; k--) {
            if (!visitedArr[y][k]) {
              res[y][k] = index++
              visitedArr[y][k] = true
              x = k
              if (x === 0) direction = 'top'
            } else {
              direction = 'top'
            }
          }
          break;
        case 'top':
          for (let k = y - 1; k >= 0; k--) {
            if (!visitedArr[k][x]) {
              res[k][x] = index++
              visitedArr[k][x] = true
              y = k
            } else {
              direction = 'right'
            }
          }
          break;
        default:
          break;
      }
    }
    return res
  };

如有更好解法，歡迎留言探討。