leetcode

leetcode 54题

Posted by franki on June 18, 2021

leetcode 54题 螺旋矩阵

给你一个 m 行 n 列的矩阵 matrix ，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：matrix = [[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：matrix = [[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]

思路

按层数输出

代码

/**
 * @param {number[][]} matrix
 * @return {number[]}
 */
function spiralOrder(matrix) {
  // 按层数输出
  const order = [];
  if (matrix.length === 0 || matrix[0].length === 0) {
    return order;
  }
  const rows = matrix.length;
  const columns = matrix[0].length;
  let left = 0, right = columns - 1, top = 0, bottom = rows - 1;
  while (left <= right && top <= bottom) {
    // 上左到上右
    for (let start = left; start <= right; start++) {
      order.push(matrix[top][start]);
    }
    // 右上到右下
    for (let start = top + 1; start <= bottom; start++) {
      order.push(matrix[start][right]);
    }
    if (left < right && top < bottom) {
      // 下右到下左
      for (let start = right - 1; start > left; start--) {
        order.push(matrix[bottom][start]);
      }
      // 左下到左上
      for (let start = bottom; start > top; start--) {
        order.push(matrix[start][left]);
      }
    }
    top++;
    left++;
    bottom--;
    right--;
  }
  return order;
}

复杂度分析:

  • 时间复杂度: O(N^2)
  • 空间复杂度：O(N)
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