Chapter 10 : Recursion.md

[Chapter 10: Recursion ] Solutions

[A]

(a) Infinite Print C adds wings to your thoughts.
(b) C adds wings to your thoughts.

[B]

(a)

  #include<stdio.h>
  #include<conio.h>

int nonrec_calc(int);
  int rec_calc(int);

  int main()
{
int num, sum;

printf("Enter a five digit number : ");
scanf("%d", &num);

sum = nonrec_calc(num);
printf("\n\nSum of digits using non-recursive function : %d\n", sum);

sum = rec_calc(num);
printf("\n\nSum of digits using recursive function: %d\n", sum);

_getch();
return 0;

}

//Non recursive function
int nonrec_calc(int num)
{
int a, sum = 0, i;
for (i = 0; num; i++)
{
	a = num % 10;//obtaining the ladt digit
	sum = sum + a;//summing up the digits
	num = num / 10;//decreasing the number by one digit
}
return (sum);
}

  //Recursive function
int rec_calc(int num)
{
int sum = 0;
if (num == 0)
	return sum;
sum = num % 10 + rec_calc(num / 10);
return sum;
}

(b)

   int func(int num);
    #include <stdio.h>
  int main()
{   int number;

printf("Enter number\n");
scanf("%d",&number);
func(number);
return 0;
  }
  int func(int num)
  {
int i;
for(i=2;i<=num;i++)
{
    if(num%i==0)
    {
        printf("%d\n",i);
        func(num/i);
        break;
    }
}
return 0;
}

(c)

  #include<stdio.h>
#include<conio.h>

void fs(int first, int second, int term);

int main()
  {
fs(0, 1, 25);
_getch();
return 0;
}

void fs(int fis, int sec, int term)
{
int num;
if (term == 0)
	return;
num = fis + sec;
fis = sec;
sec = num;
printf("%d, ", num);
fs(fis, sec, term - 1);
}

(d)

(1) Without Recursion

      void nonrec_bin(int);
      #include<stdio.h>
      int main()
      {
        int number;
        printf("Enter number\n");
        scanf("%d",&number);
        nonrec_bin(number);
        return 0;
        }
      void nonrec_bin(int num)
  {
int sum = 0;
for (; num; num /= 2)
{
	//Next digit will placed at first position.
	sum += num % 2;
	sum *= 10;
}
printf("%d", sum);
}

(2) With recursion

      #include<stdio.h>
  int bin(int);
  int main()
  {   int number;
printf("Enter number\n");
scanf("%d",&number);
bin(number);
return 0;
  }
  int bin(int number)
    {
if(number>1)
{
    bin(number/2);
}
printf("%d",number%2);

return 0;
}

(e)

int sum(int);
 int main()
  {   int number,ans;
printf("Enter number\n");
scanf("%d",&number);
ans=sum(number);
printf("%d",ans);
return 0;
  }

int sum(int x)
 {
if (x == 0)
	return x;
x = x + sum(x - 1);
return x;
  }