• [LeetCode] Unique Paths II


    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.

    Solutions:

    class Solution {
    public:
        int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) {
            if(obstacleGrid.size() < 1) return 0;
            int m = obstacleGrid.size(), n = obstacleGrid[0].size();
            int **paths = new int*[m];
            for(int i = 0;i < m;i++)
            {
                paths[i] = new int[n];
                memset(paths[i], 0, n * sizeof(int));
            }
            
            for(int i = 0;i < m;i++)
            {
                for(int j = 0;j < n;j++)
                {
                    if(i == 0 && j == 0)
                        paths[i][j] = 1 - obstacleGrid[i][j];
                    else if(obstacleGrid[i][j] == 1) 
                        paths[i][j] = 0;
                    else
                    {
                        if(i - 1 < 0) 
                        {
                            if(j - 1 < 0)
                                paths[i][j] = 0;
                            else
                                paths[i][j] = paths[i][j - 1];
                        }
                        else
                        {
                            if(j - 1 < 0)
                                paths[i][j] = paths[i - 1][j];
                            else
                                paths[i][j] = paths[i - 1][j] + paths[i][j - 1];
                        }
                    }
                }
            }
            return paths[m - 1][n - 1];
        }
    };
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  • 原文地址:https://www.cnblogs.com/changchengxiao/p/3592631.html
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