30 Day Challenge Day 13 | Leetcode 63. Unique Paths II

题解

Medium

动态规划

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