[leetcode]62. Unique Paths
[leetcode]62. Unique Paths
Analysis
周一鸭—— [每天刷题并不难0.0]
A robot is located at the top-left corner of a m x n grid (marked ‘Start’ in the diagram below).
The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked ‘Finish’ in the diagram below).
How many possible unique paths are there?
Implement
方法一
class Solution {
public:
int uniquePaths(int m, int n) {
vector<vector<int>> res(m, vector<int>(n, 1));
for(int i=1; i<m; i++){
for(int j=1; j<n; j++)
res[i][j] = res[i-1][j] + res[i][j-1];
}
return res[m-1][n-1];
}
};
方法二(space optimization)
class Solution {
public:
int uniquePaths(int m, int n) {
if(m==0 && n==0)
return 0;
vector<int> dp(n, 1);
for(int i=1; i<m; i++){
for(int j=1; j<n; j++)
dp[j] += dp[j-1];
}
return dp[n-1];
}
};