✅54. 螺旋矩阵

[bazinga-web]

54. 螺旋矩阵

给定一个包含 m x n 个元素的矩阵（m 行, n 列），请按照顺时针螺旋顺序，返回矩阵中的所有元素。

示例 1:

输入:
[
 [ 1, 2, 3 ],
 [ 4, 5, 6 ],
 [ 7, 8, 9 ]
]
输出: [1,2,3,6,9,8,7,4,5]

示例 2:

输入:
[
  [1, 2, 3, 4],
  [5, 6, 7, 8],
  [9,10,11,12]
]
输出: [1,2,3,4,8,12,11,10,9,5,6,7]

[bazinga-web]

解题思路：

1. 如果数组为空，则返回空数组
2. 定义四个边界及当前方向
3. 当左边界小于等于右边界，且上边界小于等于下边界时，
   执行while循环：按照右下左上的顺序，依次将经过的
   字符添加到结果中
4. while循环结束返回结果

/**
 * @param {number[][]} matrix
 * @return {number[]}
 */
var spiralOrder = function (matrix) {
  let result = [];
  if (matrix.length === 0) return result;
  let left = 0,
    right = matrix[0].length - 1,
    top = 0,
    bottom = matrix.length - 1,
    direction = "right";
  while (left <= right && top <= bottom) {
    if (direction === "right") {
      for (let i = left; i <= right; i++) {
        result.push(matrix[top][i]);
      }
      top++;
      direction = "down";
    } else if (direction === "down") {
      for (let i = top; i <= bottom; i++) {
        result.push(matrix[i][right]);
      }
      right--;
      direction = "left";
    } else if (direction === "left") {
      for (let i = right; i >= left; i--) {
        result.push(matrix[bottom][i]);
      }
      bottom--;
      direction = "top";
    } else if (direction === "top") {
      for (let i = bottom; i >= top; i--) {
        result.push(matrix[i][left]);
      }
      left++;
      direction = "right";
    }
  }
  return result;
};

[Ray-56]

方向遍历解

/**
 * @param {number[][]} matrix
 * @return {number[]}
 */
var spiralOrder = function(matrix) {
	if (!matrix.length) return [];
	let ret = [];
	let top = 0;
	let bottom = matrix.length - 1;
	let left = 0;
	let right = matrix[0].length - 1;
	let direction = 'right';

	while (left <= right && top <= bottom) {
		if (direction == 'right') {
			for (let i = left ; i <= right; i++) {
				ret.push(matrix[top][i]);
			}
			direction = 'bottom';
			top++;
		} else if (direction == 'bottom') {
			for (let i = top; i <= bottom; i++) {
				ret.push(matrix[i][right]);
			}
			direction = 'left';
			right--;
		} else if (direction == 'left') {
			for (let i = right; i >= left; i--) {
				ret.push(matrix[bottom][i]);
			}
			direction = 'top';
			bottom--;
		} else if (direction == 'top') {
			for (let i = bottom; i >= top; i--) {
				ret.push(matrix[i][left]);
			}
			direction = 'right';
			left++;
		}
	}

	return ret;
};