StairsProblem.c

// A C program to count number of ways to reach n't stair when 
// a person can climb 1 or 2 stairs at a time.

//if code is wrong or i misssed a case please let me know. If code can be optmised or logic can be reformed please let me know.

#include<stdio.h>
int one = 0;
int two = 0;
int count = 0;

int fact(int n){
    int fact = 1;
    for (int i =1; i<=n;i++){
        fact = fact *i;
    }
    return fact;
}

int stairs(int n, int two, int one){
    
    if(one == 0 || one ==1){
        count = 1;
        return count;
        
    }
    else{        
        stairs(n-1,two+1,(one-2));
        count = count + fact(n-1)/(fact(two+1)*fact(one-2));
        return count;
    }
    
}

int main(){
    int n = 20;
    printf("%d",stairs(n,two,n));
    
}