63. 不同路径 II(dp)(Leetcode)

63. 不同路径 II

class Solution {
public:
    int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
        int m = obstacleGrid.size(); 
        int n = obstacleGrid[0].size();
        vector<vector<int>> ans(m, vector<int>(n));
        if(obstacleGrid[0][0]) return 0; 
        for(int i = 0; i < m; ++i){
            for(int j = 0; j < n; ++j){
                if(!obstacleGrid[i][j]){
                    if(!i && !j) ans[i][j] = 1;
                    else{
                        if(i) ans[i][j] += ans[i-1][j];
                        if(j) ans[i][j] += ans[i][j-1];
                    }
                }
            }
        }
        return ans[m-1][n-1];
    }
};