leetcode刷题笔记(Golang)--62. Unique Paths

62. Unique Paths

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?

Above is a 7 x 3 grid. How many possible unique paths are there?

Note: m and n will be at most 100.

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

func uniquePaths(m int, n int) int {
	paths := make([][]int, n+1)
	for i := range paths {
		paths[i] = make([]int, m+1)
	}
	paths[1][1] = 1

	for i := 1; i <= n; i++ {
		for j := 1; j <= m; j++ {
			if i == 1 && j == 1 {
				continue
			} else {
				paths[i][j] = paths[i-1][j] + paths[i][j-1]
			}
		}
	}
	return paths[n][m]
}