1706

class Solution {
public:
    int rsize, csize;
    vector<int> findBall(vector<vector<int>>& grid) {
        rsize = grid.size(); csize = grid[0].size();
        vector<int> ans(csize);
        for(int i=0; i<csize; i++)
            ans[i] = dfs(0, i, grid);
        return ans;
    }

    bool check(int r, int c){
        if(r<0 || c<0 || r>=rsize || c>=csize) return false;
        return true;
    }

    int dfs(int r, int c, vector<vector<int>> &grid){
        // If last row is exited.
        if(r == rsize)
            return c;

        // Current cell should be valid.
        if(check(r, c)){
            // Check for direction of adjacent cell and also it's validity.
            if(grid[r][c] == 1 && check(r, c+1) && grid[r][c+1] == 1)
                return dfs(r+1, c+1, grid);
            else if(grid[r][c] == -1 && check(r, c-1) && grid[r][c-1] == -1)
                return dfs(r+1, c-1, grid);
        }

        // Return -1 if no condition is applicable and the ball is stuck.
        return -1;
    }
};