LeetCode-in-All
70. Climbing Stairs
Easy
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 step + 1 step
-
2 steps
Example 2:
Input: n = 3
Output: 3
Explanation: There are three ways to climb to the top.
-
1 step + 1 step + 1 step
-
1 step + 2 steps
-
2 steps + 1 step
Constraints:
1 <= n <= 45
Solution
impl Solution {
pub fn climb_stairs(n: i32) -> i32 {
if n < 2 {
return n;
}
let n = n as usize;
let mut cache = vec![0; n];
// Base cases
cache[0] = 1;
cache[1] = 2;
// Fill the cache using dynamic programming
for i in 2..n {
cache[i] = cache[i - 1] + cache[i - 2];
}
cache[n - 1]
}
}