You are climbing a staircase. It takes n steps to reach the top.
Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
Example 1:
Input: n = 2 Output: 2 Explanation: There are two ways to climb to the top. 1. 1 step + 1 step 2. 2 steps
Example 2:
Input: n = 3 Output: 3 Explanation: There are three ways to climb to the top. 1. 1 step + 1 step + 1 step 2. 1 step + 2 steps 3. 2 steps + 1 step
Constraints:
1 <= n <= 45struct Solution;
impl Solution {
fn climb_stairs(n: i32) -> i32 {
match n {
1 | 2 => n,
k => (2..k).fold((1, 2), |acc, _| (acc.1, acc.0 + acc.1)).1,
}
}
}
#[test]
fn test() {
assert_eq!(Solution::climb_stairs(3), 3);
assert_eq!(Solution::climb_stairs(2), 2);
assert_eq!(Solution::climb_stairs(1), 1);
}