LeetCode 58 Spiral Matrix II

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.

For example,
Given n = 3,

You should return the following matrix:

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

思路：与上一篇类似，只要不越界就ok

public class Solution {public int[][] generateMatrix(int n) {    if (n == 0)return new int[0][0];int[][] matrix = new int[n][n];int x1 = 0;int y1 = 0;int x2 = matrix.length - 1;int y2 = matrix[0].length - 1;int i = 0, j = 1;while (x1 <= x2 && y1 <= y2) {// up rowfor (i = y1; i <= y2; ++i, j++)matrix[x1][i] = j;// right columnfor (i = x1 + 1; i <= x2; ++i, j++)matrix[i][y2] = j;// bottom rowfor (i = y2 - 1; x2 != x1 && i >= y1; --i, j++)matrix[x2][i] = j;// left columnfor (i = x2 - 1; y1 != y2 && i > x1; --i, j++)matrix[i][y1] = j;x1++;y1++;x2--;y2--;}return matrix;}}