class Solution {public:    int num[110][110];    int dfs(int m,int n,int x,int y)    {        if(num[x][y]) return num[x][y];        if(x==m-1 && y==n-1) return 1;        if(x+1<m) num[x][y]+=dfs(m,n,x+1,y);        if(y+1<n) num[x][y]+=dfs(m,n,x,y+1);        return num[x][y];    }    int uniquePaths(int m, int n) {        memset(num,0,sizeof(num));        return dfs(m,n,0,0);    }};