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;

    }

};