Problem

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

Input: 2
Output: 2
Explanation: There are two ways to climb to the top.
1. 1 step + 1 step
2. 2 steps

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

Code

static int var = [](){
    std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    return 0;
}();
class Solution {
public:
    int climbStairs(int n) {

        if(n==0)
            return 1;
        else if(n==1)
            return 1;
        int left = 1;
        int right = 1;
        int temp = 0;
        for(int i = 2;i <= n;i++){
            temp = left + right;
            right = left;
            left = temp;
            
        }
        return temp;
    }
};

Result

70. Climbing Stairs.png