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  • [leetcode-63-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.

    思路:

    类似于

    leetcode-62-Unique Paths中提到的方法,仅需判断当前格子是否是障碍即可。

    如果是第一行或者第一列的障碍,那么将它之后所有格子置为0。

    如果不是第一行或者第一列的话,仅需将它置为0。

    int uniquePathsWithObstacles(vector<vector<int>>& grid)
        {
            //类似没有障碍的方法:将有障碍的地方置为0;
            if (grid.empty())return 0;
            int row = grid.size();
            int col = grid[0].size();
            if (grid[0][0] == 1)return 0;
            
            for (int i = 0; i < col;i++)//处理第一行
            {
                if (grid[0][i] == 0)grid[0][i] = 1;            
                else if (grid[0][i] == 1)
                {
                    for (int j = i; j < col; j++)
                        grid[0][j] = 0;//i之后都置为0;
                    i = col;
                }                
            }
            for (int i = 1; i < row; i++)//处理第一列
            {
                if (grid[i][0] == 0)grid[i][0] = 1;
                else if (grid[i][0] == 1)
                {
                    for (int j = i; j < row; j++)
                        grid[j][0] = 0;//i之后都置为0;
                    i = row;
                }
            }
            for (int i = 1; i < row; i++)
            {
                for (int j = 1; j < col; j++)
                {
                    if (grid[i][j] == 0)//不是障碍
                    {                                
                        grid[i][j] = grid[i - 1][j] + grid[i][j - 1];                    
                    }
                    else if(grid[i][j] == 1)grid[i][j] = 0;
                }
            }
            return grid[row - 1][col - 1];
        }
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  • 原文地址:https://www.cnblogs.com/hellowooorld/p/6511305.html
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