记录一下，觉得倒水思想来做 总体看起来还是比较清晰的。

class Solution {
public:
    vector<vector<int>> generateMatrix(int n) {
        int a[4][2] = {{0,1}, {1,0}, {0,-1},{-1,0}};

        int direction=0;  //方向
        int num=0;

        int S =n*n;
        int x = 0;
        int y = 0;
        
        vector<vector<int>> Matrix(n, vector<int>(n, 0));

        while(num!=S){
            num++;
            Matrix[x][y]=num;

            x+=a[direction][0];
            y+=a[direction][1];
            if(x>=n || y>=n || x<0 || y<0 || Matrix[x][y]!=0){
                x-=a[direction][0];
                y-=a[direction][1];
                direction = (direction+1)%4;
                x+=a[direction][0];
                y+=a[direction][1];
            } 
        }  
        return  Matrix;

    }
};