力扣 59. 螺旋矩阵 II 模拟 水

https://leetcode-cn.com/problems/spiral-matrix-ii/

思路：昨天代码改一下就完事了。

class Solution {
    
    
public:
    vector<vector<int>> generateMatrix(int n) {
    
    
        vector<vector<int>> ans(n,vector<int>(n));
        int left=0,right=n-1,top=0,down=n-1,val=0;
        while(left<=right&&top<=down)
        {
    
    
            for(int i=left;i<=right;i++)
                ans[top][i]=++val;
            ++top;
            for(int i=top;i<=down;i++)
                ans[i][right]=++val;
            --right;
            for(int i=right;i>=left;i--)
                ans[down][i]=++val;
            --down;
            for(int i=down;i>=top;i--)
                ans[i][left]=++val;
            ++left;
        }
        return ans;
    }
};