> For the complete documentation index, see [llms.txt](https://soumyajit4419.gitbook.io/ds-algo/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://soumyajit4419.gitbook.io/ds-algo/dynamic-programming/climbing-stairs.md).

# 2.Climbing Stairs

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?

### Climbing stairs follows Fibonacci series approach.

```cpp
class Solution
{
public:
    int climbStairs(int n)
    {

        if(n==1){return 1;}
        int a = 1, b = 1, s = 0;
        

        for (int i = 2; i <= n; i++)
        {
            s = a + b;
            a = b;
            b = s;
        }

        return s;
    }
};
```

## Count ways to N'th Stair(Order does not matter)

Order does not matter means for n=4 {1 2 1},{2 1 1},{1 1 2} are considered same.

### Solution:&#x20;

Approach\
Count increases when number are even

```cpp
class Solution
{
public:
    //Function to count number of ways to reach the nth stair
    //when order does not matter.
    long long countWays(int n)
    {
        // your code here
        long long int count = 1;
        for (int i = 1; i <= n; i++)
        {
            if (i % 2 == 0)
            {
                count++;
            }
        }

        return count;
    }
};
```