Spiral Matrix II

问题：蛇形矩阵
分析：设置变量dir，0123分别代表方向右下左上

class Solution {
public:
    int num[300][300];
    void dfs(int x,int y,int k,int n,int dir)
    {
        num[x][y]=k;
        if(k>=n*n) return ;//这里要用大于,n=0会一直不出现等于
        if(dir==0) 
        {
            if(y+1<n && num[x][y+1]==0 ) dfs(x,y+1,k+1,n,0);
            else dfs(x+1,y,k+1,n,1);//如果右边不能走，就走下边
        }
        if(dir==1)
        {
            if( x+1<n && num[x+1][y]==0) dfs(x+1,y,k+1,n,1);
            else dfs(x,y-1,k+1,n,2);
        }
        if(dir==2)
        {
            if(y-1>=0 && num[x][y-1]==0) dfs(x,y-1,k+1,n,2);
            else dfs(x-1,y,k+1,n,3);
        }
        if(dir==3)
        {
            if(x-1>=0 && num[x-1][y]==0) dfs(x-1,y,k+1,n,3);
            else dfs(x,y+1,k+1,n,0);
        }
    }
    vector<vector<int> > generateMatrix(int n) {
       // memset(num,0,sizeof(num));
        vector<vector<int> >vec1;
       dfs(0,0,1,n,0);
        for(int i=0;i<n;i++)
        {
            vector<int> vec2;
            for(int j=0;j<n;j++)
            {
                vec2.push_back(num[i][j]);
            }
            vec1.push_back(vec2);
        }
        return vec1;
    }
};