980. Unique Paths III

class Solution {
public:
int stx;
int sty;
int edx;
int edy;
int pathse;
int m;
int n;
int ans=0;

void dfs(vector<vector<int>> grid,int i,int j, int path){
    if(i<0 || j<0 || i>=m || j>=n || grid[i][j]==-1)return ;
    if(i==edx && j==edy && path==pathse){
        ans++;
        return ;
    }
    grid[i][j]=-1;
    dfs(grid,i+1,j,path+1);
    dfs(grid,i-1,j,path+1);
    dfs(grid,i,j+1,path+1);
    dfs(grid,i,j-1,path+1);
}
    int uniquePathsIII(vector<vector<int>>& grid) {
        m=grid.size();
        n=grid[0].size();
        pathse=m*n;
        for(int i=0;i<m;i++){
            for(int j=0;j<n;j++){
                if(grid[i][j]==1){
                    stx=i;
                    sty=j;
                }
                else if(grid[i][j]==2){
                    edx=i;
                    edy=j;
                }
                else if(grid[i][j]==-1){
                    pathse--;
                }
            }
        }
        dfs(grid,stx,sty,1);
        return ans;
    }
};