LeetCode-in-All
62. Unique Paths
Medium
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 = 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
Example 3:
Input: m = 7, n = 3
Output: 28
Example 4:
Input: m = 3, n = 3
Output: 6
Constraints:
1 <= m, n <= 100- It’s guaranteed that the answer will be less than or equal to
2 * 109.
Solution
class Solution {
fun uniquePaths(m: Int, n: Int): Int {
val dp = Array(m) { IntArray(n) }
for (i in 0 until m) {
dp[i][0] = 1
}
for (j in 0 until n) {
dp[0][j] = 1
}
for (i in 1 until m) {
for (j in 1 until n) {
dp[i][j] = dp[i - 1][j] + dp[i][j - 1]
}
}
return dp[m - 1][n - 1]
}
}