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LeetCode 63: Unique Paths II

2015-10-30 13:37 519 查看

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.

解题思路

class Solution {
public:
int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
if (obstacleGrid.size() == 0 || obstacleGrid[0].size() == 0 || obstacleGrid[0][0] == 1)
return 0;

int m = obstacleGrid.size(), n = obstacleGrid[0].size();
vector<vector<int>> dp(m+1, vector<int>(n+1, 0));
dp[1][1] = 1;
for (int i = 1; i <= m; ++i) {
for (int j = 1; j <= n; ++j) {
if ((i != 1 || j != 1 ) && obstacleGrid[i-1][j-1] == 0) {
dp[i][j] = dp[i-1][j] + dp[i][j-1];
}
}
}

return dp[m]
;
}
};
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标签:  leetcode