leetcode

leetcode 59题

Posted by franki on June 22, 2021

leetcode 59题 螺旋矩阵 II

给你一个正整数 n ，生成一个包含 1 到 n2 所有元素，且元素按顺时针顺序螺旋排列的 n x n 正方形矩阵 matrix 。

示例1

输入：n = 3
输出：[[1,2,3],[8,9,4],[7,6,5]]

示例2

输入：n = 1
输出：[[1]]

思路

顺时针打印，控制上下左右的边界

代码

/**
 * @param {number} n
 * @return {number[][]}
 */
function generateMatrix(n) {
    const maxNum = n * n;
    let curNum = 1;
    const matrix = new Array(n).fill(0).map(() => new Array(n).fill(0));
    let row = 0, column = 0;
    const directions = [[0, 1], [1, 0], [0, -1], [-1, 0]];
    let directionIndex = 0;
    while (curNum <= maxNum) {
        matrix[row][column] = curNum;
        curNum++;
        const nextRow = row + directions[directionIndex][0], nextColumn = column + directions[directionIndex][1];
        if (nextRow < 0 || nextRow >= n || nextColumn < 0 || nextColumn >= n || matrix[nextRow][nextColumn] !== 0) {
            directionIndex = (directionIndex + 1) % 4;
        }
        row = row + directions[directionIndex][0];
        column = column + directions[directionIndex][1];
    }
    return matrix;
}

复杂度分析:

  • 时间复杂度: O(N)
  • 空间复杂度：O(N^2)
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