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  • 【LeetCode】063. Unique Paths II

    题目:

    Follow up for "Unique Paths":

    Now consider if some obstacles are added to the grids. How many unique paths would there be?

    An obstacle and empty space is marked as 1 and 0 respectively in the grid.

    For example,

    There is one obstacle in the middle of a 3x3 grid as illustrated below.

    [
      [0,0,0],
      [0,1,0],
      [0,0,0]
    ]
    

      

    The total number of unique paths is 2.

    Note: m and n will be at most 100.

    题解:

    Solution 1 ()(未优化)

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

    Solution 2 ()

    class Solution {
    public:
        int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
            if(obstacleGrid.empty() || obstacleGrid[0].empty()) return 0;
            int m = obstacleGrid.size(), n = obstacleGrid[0].size();
            vector<int> dp(n,0);
            dp[0] = 1;
            for(int i=0; i<m; ++i) {
                for(int j=0; j<n; ++j) {
                    if(obstacleGrid[i][j] == 1)    
                        dp[j] = 0;
                    else {
                        if(j > 0)
                            dp[j] += dp[j-1];
                    }
                }
            }    
            return dp[n-1];
        }
    };
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  • 原文地址:https://www.cnblogs.com/Atanisi/p/6817007.html
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