LeetCode in TypeScript
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
function uniquePaths(m: number, n: number): number {
let aboveRow = Array(n).fill(1)
for (let row = 1; row < m; row++) {
let currentRow = Array(n).fill(1)
for (let col = 1; col < n; col++) {
currentRow[col] = currentRow[col - 1] + aboveRow[col]
}
aboveRow = currentRow
}
return aboveRow[n - 1]
}
export { uniquePaths }