No.213 - LeetCode[63] Unique Paths II - 矩阵左上走右下的路径数 - 经典dp

/*
 * @lc app=leetcode id=63 lang=cpp
 *
 * [63] Unique Paths II
 */

// @lc code=start
class Solution {
public:
    int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
        int N = obstacleGrid.size();
        if(N <= 0) return 0;
        int M = obstacleGrid[0].size();
        if(M <= 0) return 0;
        vector<vector<int>> dp(N+1,vector<int>(M+1,0));
        if(obstacleGrid[0][0] == 0) dp[1][1] = 1;
        for(int i=1;i<=N;i++){
            for(int j=1;j<=M;j++){
                if(obstacleGrid[i-1][j-1] == 0)
                    dp[i][j] += dp[i-1][j] + dp[i][j-1];
            }
        }
        return dp[N][M];
    }
};
// @lc code=end