LeetCode 62. Unique Paths
Woodyiiiiiii opened this issue · comments
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?
Example 1:
Input: m = 3, n = 2
Output: 3
Explanation:
From the top-left corner, there are a total of 3 ways to reach the bottom-right corner:
1. Right -> Right -> Down
2. Right -> Down -> Right
3. Down -> Right -> Right
Example 2:
Input: m = 7, n = 3
Output: 28
空间一维dp数组:
class Solution {
public int uniquePaths(int m, int n) {
// space : O(n);
int[] dp = new int[n];
dp[0] = 1;
for (int i = 1; i < n; ++i) {
dp[i] += dp[i - 1];
}
for (int i = 1; i < m; ++i) {
for (int j = 1; j < n; ++j) {
dp[j] += dp[j - 1];
}
}
return dp[n - 1];
}
}
参考资料:
LeetCode原题