[Leetcode] 59. 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 ]]

public class Solution {    public int[][] generateMatrix(int n) {        int[][] result = new int[n][n];        int num = 1;        for(int layer = 0; layer * 2 < n; layer++){            for(int i = layer; i < n - layer; i++){                result[layer][i] = num++;            }            for(int i = layer + 1; i < n - layer; i++){                result[i][n - layer - 1] = num++;            }            for(int i = n - layer - 2; i >= layer; i--){                result[n - layer - 1][i] = num++;            }            for(int i = n - layer - 2; i >= layer + 1; i--){                result[i][layer] = num++;            }        }        return result;    }}