59. Spiral Matrix II 解题记录

题目描述：

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 ]
]

解题思路：

这题的解题思路和Spiral Matrix是一样的，而且col和row相同的情况反而更简单了。

代码：

class Solution {
public:
    vector<vector<int>> generateMatrix(int n) {
        vector<vector<int>> ret(n, vector<int>(n, 1));
        int val = 1, times = n/2;
        for(int i = 0; i < times; i++){
            for(int j = i; j < n-1-i; j++)
                ret[i][j] = val++;
            for(int j = i; j < n-1-i; j++)
                ret[j][n-1-i] = val++;
            for(int j = n-1-i; j > i; j--)
                ret[n-1-i][j] = val++;
            for(int j = n-1-i; j > i; j--)
                ret[j][i] = val++;
        }
        if(n%2 == 1)
            ret[times][times] = val;
        return ret;
    }
};