package algorithms

//You are climbing a stair case. It takes n steps to reach to the top.
//
//Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
//
//Note: Given n will be a positive integer.
//
//
//Example 1:
//
//Input: 2
//Output:  2
//Explanation:  There are two ways to climb to the top.
//
//1. 1 step + 1 step
//2. 2 steps
//Example 2:
//
//Input: 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

func climbStairs(n int) int {
	if n <= 1 {
		return n
	}
	pre, cur := 1, 1
	for i := 1; i < n; i++ {
		pre, cur = cur, pre+cur
	}
	return cur
}