Spiral Matrix II

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 ]]

解析：

一圈一圈的填充数组，顺时针方向，注意边界条件。

代码：

class Solution {public:    vector<vector<int>> generateMatrix(int n) {        vector<vector<int>>ans(n,vector<int>(n));                int k=1;        int i=0;        int j=0;        while(k<=n*n)        {            j=i;            while(j<(n-i))            {                ans[i][j]=k++;                 j++;            }            j=i+1;            while(j<(n-1-i))            {                ans[j][n-1-i]=k++;                j++;            }            j=n-1-i;            while(j>i)            {                ans[n-i-1][j]=k++;                j--;            }            j=n-i-1;            while(j>i)            {                ans[j][i]=k++;                j--;            }            i++;        }        return ans;    }};