LeetCode 63 Unique Paths II DP
You are given an m x n integer array grid. There is a robot initially located at the top-left corner (i.e., grid[0][0]). The robot tries to move to the bottom-right corner (i.e., grid[m-1][n-1]). The robot can only move either down or right at any point in time.
An obstacle and space are marked as 1 or 0 respectively in grid. A path that the robot takes cannot include any square that is an obstacle.
Return the number of possible unique paths that the robot can take to reach the bottom-right corner.
The testcases are generated so that the answer will be less than or equal to 2 * 109.
Solution
显然设 \(dp[i][j]\) 表示到 \(grid[i][j]\) 的方案数，转移方程：
\[dp[i][j] = dp[i-1][j]+dp[i][j-1] \]点击查看代码
class Solution {
private:
int dp[103][103];
public:
int uniquePathsWithObstacles(vector>& obstacleGrid) {
int n = obstacleGrid.size(), m = obstacleGrid[0].size();
if(n==1 && m==1){
if(obstacleGrid[0][0]==1) return 0;
else return 1;
}
if(obstacleGrid[0][0]==1)return 0;
else dp[0][0]=1;
for(int i=1;i