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) { if(n<0) return null; int[][] res = new int[n][n]; int start = 1, left = 0 , right = 0 ; for(int i = n ; i>0 ; i-=2 ){ if(i==1) { res[left][right] = start; } else{ for(int j = 0 ; j<i-1;j++){ res[left][right++] = start++; } for(int j = 0; j< i-1;j++){ res[left++][right] = start++; } for(int j = 0; j< i-1;j++){ res[left][right--] = start++; } for(int j = 0; j< i-1;j++){ res[left--][right] = start++; } left++; right++; } } return res; } }