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【LeetCode】Unique Paths II

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.

 

与上题差别不大,只需要判断有障碍置零即可。

对于首行首列,第一个障碍及之后的路径数均为0

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

【LeetCode】Unique Paths II