980. Unique Paths III

class Solution {
public:
    void BFS(int i,int j, int& num, int& count, const int &row, const int &col, const int & numWalk, vector<vector<int>>& grid, vector<vector<int>>& visited){
        //cout << "i = " << i << ",j = " << j << ",visited =" << visited[i][j] << endl;
        if(i < 0 || i >= row || j < 0 || j >= col){
            return;
        }
        if(grid[i][j] == -1){
            return;
        }
        if(grid[i][j] == 2){
            if(count == numWalk){
                num++;
            }
            return;
        }
        if(visited[i][j] == 0){
            visited[i][j] = 1;
            if(grid[i][j] == 0){
                count++;
            }
        }else{
            return;
        }

        BFS(i+1,j,num,count,row,col,numWalk,grid,visited);
        BFS(i-1,j,num,count,row,col,numWalk,grid,visited);
        BFS(i,j-1,num,count,row,col,numWalk,grid,visited);
        BFS(i,j+1,num,count,row,col,numWalk,grid,visited);
        if(grid[i][j] == 0){
            count--;
            visited[i][j] = 0;
        }else{
            return;
        }
                
    }
    
    int uniquePathsIII(vector<vector<int>>& grid) {
        int row = grid.size(), col = grid[0].size(), i = 0, j = 0, count = 0, num = 0, numWalk = 0;       
        int start_x = 0, start_y = 0, end_x = 0, end_y = 0;
        // vector<vector<vector<int>>> path(row,vector<int>(col,vector<int>(4));
        vector<vector<int>> visited(row,vector<int>(col));
        // cout << visited.size() << endl;
        // cout << visited[0].size() << endl;
        
        for(i = 0; i < row; i++){
            for(j = 0; j < col; j++){
                if(grid[i][j] == 1){
                    start_x = i;
                    start_y = j;
                }else if(grid[i][j] == 2){
                    end_x = i;
                    end_y = j;
                }else if(grid[i][j] == 0){
                    numWalk++;
                }
            }
        }
        
        //visited[start_x][start_y] = 1;
        BFS(start_x,start_y,num,count,row,col,numWalk,grid,visited);
        return num;
        
        
        
    }
};