recursion.java

import java.util.*;

public class recursion {
    public static void printdecen(int n){
        if (n==0){
            return;
        }
        System.out.println(n);
        printdecen(n-1);
    }
    public static void printascen(int m){
        if (m==6){
            return;
        }
        System.out.println(m);
        printascen(m+1);
    }
    public static void sumOfNum(int a,int n1,int sum){
        if (a==n1+1){
            System.out.println(sum);
            return;
        }
        sum=sum+a;
        System.out.print(sum+" ");
        sumOfNum(a+1,n1,sum);
    }
    public static void facOfNum(int a,int n1,int fac){
        if (a==n1+1){
            System.out.println(fac);
            return;
        }
        fac=fac*a;
        System.out.print(fac+" ");
        facOfNum(a+1,n1,fac);
    }
    public static void fibonacci(int x,int y,int n2){
       if(n2==0){
        return;
       }
       int c=x+y;
       System.out.print(c+" ");
       fibonacci(y, c, n2-1);
    }
    public static int calPower(int c,int d){
      if (d==0){
        return 1;
      }
      if(c==0){
        return 0;
      }
      int cpowdm1=calPower(c, d-1);
      int cpowd=c*cpowdm1;
      return cpowd;
    }
    public static int calPower2(int c,int d){
        if (d==0){
          return 1;
        }
        if(c==0){
          return 0;
        }
        if(d%2==0){
            return calPower2(c, d/2)* calPower(c, d/2);
        }else{
            return calPower(c, d/2)* calPower(c, d/2)* c;
        }
      }
   

    public static void main(String args[]){
        Scanner sc=new Scanner(System.in);
        int n1=sc.nextInt();
        int a=1;
        int sum=0 ;
        int fac=1;
        sumOfNum(a,n1,sum);
        facOfNum(a,n1,fac);
        int x=0,y=1,n2=7;
        System.out.print(x+" "+y+" ");
        fibonacci(x, y, n2-2);
        System.out.println(" ");
        int n=5;
        printdecen(n);
        int m=1;
        printascen(m);
        int c=2,d=5;
        int ans=calPower(c, d);
        System.out.println(ans);//height is n
        int ans2=calPower2(c, d);
        System.out.println(ans2);//height is logn
        
    }
    
}
//print x^n (stack height=n)???