題目鏈接

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.

解題思路

TODO （稍后補充）

解題代碼

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