leetcode 63. Unique Paths II

题意

在一个矩阵中只能向右和向下走且不能走有障碍的点，问从起点到终点有多少种走法

题解

使用动态规划。

dp[i][j] = 0; （obstacleGrid[i][j] == 1）

dp[i][j] = dp[i - 1][j] + dp[i][j - 1];

代码

class Solution {
public:
int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {

int m = obstacleGrid.size(), n = obstacleGrid[0].size();
if(obstacleGrid[0][0] == 1)
return 0;
int dp[m]
;
dp[0][0] = 1;
for(int j = 1; j < n; j++)
{
if(obstacleGrid[0][j] == 1)
dp[0][j] = 0;
else
dp[0][j] = dp[0][j - 1];
}
for(int i = 1; i < m; i++)
{
if(obstacleGrid[i][0] == 1)
dp[i][0] = 0;
else
dp[i][0] = dp[i - 1][0];
}
for(int i = 1; i < m; i++)
{
for(int j = 1; j < n; j++)
{
if(obstacleGrid[i][j] == 1)
dp[i][j] = 0;
else
dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
}
}
return dp[m - 1][n - 1];

}
};