Climbing stairs

Math Dynamic Programming Memoization

53.9% acceptance

Jan 12, 2026

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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?

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn climb_stairs(n: i32) -> i32 {
    if n <= 2 {
      return n;
    }
    
    let mut prev2 = 1;
    let mut prev1 = 2;
    
    for _ in 3..=n {
      let curr = prev1 + prev2;
      prev2 = prev1;
      prev1 = curr;
    }
    
    prev1
  }
}