力扣--59.螺旋矩阵II

 

 

模拟顺时针画矩阵的过程:

• 填充上行从左到右
• 填充右列从上到下
• 填充下行从右到左
• 填充左列从下到上

由外向内一圈一圈这么画下去

/*** 生成一个包含从1到n*n的数字的矩阵* @param {number} n - 矩阵的大小，为正整数* @return {number[][]} - 返回一个n x n的二维数组，数组中的每个元素为从1到n*n的递增数字*/
var generateMatrix = function (n) {
let matrix = new Array(n);for (let i = 0; i < n; i++) {matrix[i] = new Array(n).fill(0);}let top = 0, bottom = n - 1, left = 0, right = n - 1;let direction = [[-1, 0], [0, 1], [1, 0], [0, -1]]; // 上、右、下、左四个方向let index = 0;while (top <= bottom && left <= right) {// 沿着当前方向遍历边界for (let i = left; i <= right; i++) {matrix[top][i] = ++index;}top++;for (let i = top; i <= bottom; i++) {matrix[i][right] = ++index;}right--;if (top <= bottom) {for (let i = right; i >= left; i--) {matrix[bottom][i] = ++index;}bottom--;}if (left <= right) {for (let i = bottom; i >= top; i--) {matrix[i][left] = ++index;}left++;}}return matrix;
};