[99클럽 코테 스터디 40일차 TIL] Unique Paths

💡문제

https://leetcode.com/problems/unique-paths/

There is a robot on an m x n grid. The robot is 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.

Given the two integers m and n, return the number of possible unique paths that the robot can take to reach the bottom-right corner.

The test cases are generated so that the answer will be less than or equal to 2 * 109.

Example 1:

 

Input: m = 3, n = 7
Output: 28

Example 2:

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 -> Down -> Down
2. Down -> Down -> Right
3. Down -> Right -> Down

Constraints:

• 1 <= m, n <= 100

 

💡키워드

• 동적계획법

 

💡접근/해결 방법

✅ 풀이

class Solution:
    def uniquePaths(self, m: int, n: int) -> int:
        sum = n + m - 2
        ans = 1
        choose = min(m,n) - 1
        
        for i in range(1, choose + 1):
            ans = ans *  sum / i
            sum -= 1

        return int(ans)