Leetcode59螺旋矩阵2

代码：

class Solution {public int[][] generateMatrix(int n) {if(n==1){int[][] arr = {{1}};return arr; }int[][] arr = new int[n][n];int cnt=1;int left = 0,right = n-1,top=0,down=n-1;while(left<right){for(int i=left;i<right;i++){arr[top][i] = cnt++;}for(int j=top;j<down;j++){arr[j][right] = cnt++;}for(int i=right;i>left;i--){arr[down][i] = cnt++;}for(int j=down;j>top;j--){arr[j][left] = cnt++;}left++;right--;top++;down--;}if(cnt==n*n){arr[left][top] = n*n;}return arr;}
}