Let's see the Concept of Recursion in 12 usefull Program in C language .
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Basic For Loop program in c language
Top 10 Basic C Programs For Beginners
1.Program for Adding Two Numbers Using Recursion.
#include<stdio.h>
int y;
/*
Function to add two numbers and
return the result
*/
int add(int m, int n)
{
if(n == 0)
return m;
/*
Recursion: adding 1, n times and
then at the end adding m to it
*/
y = add(m, n-1) + 1;
return y; // return the result
}
int main()
{
printf("\n\n\t\tStudytonight - Best place to learn\n\n\n");
int a, b, r;
printf("Enter the two numbers:\n");
scanf("%d%d", &a, &b);
r = add(a, b); // function call
printf("\n\nSum of two numbers is: %d\n\n", r);
printf("\n\n\t\t\tCoding is Fun !\n\n\n");
return 0;
}
2.Program to find Factorial of a Number using Recursion.
#include<stdio.h>
// declaring the function
int fact(int);
int main()
{
printf("\n\n\t\tStudytonight - Best place to learn\n\n\n");
int num, f;
printf("\n\nEnter a number: ");
scanf("%d", &num);
f= fact(num);
printf("\n\nFactorial of %d is %d\n\n", num, f);
printf("\n\n\t\t\tCoding is Fun !\n\n\n");
return 0;
}
int fact(int aj)
{
if(aj==1 || aj==0)
return 1;
else
return (aj*fact(aj-1));
}
3.Program to print Fibonacci Series using Recursion.
A Fibonacci series is defined as a series in which each number is the sum of the previous two numbers with 1, 1 being the first two elements of the series.
#include<stdio.h>
// declaring the function
void printFibo(int );
int main()
{
printf("\n\n\t\tStudytonight - Best place to learn\n\n\n");
int k, n;
long int i = 0, j = 1;
printf("Enter the length of the Fibonacci series: ");
scanf("%d", &n);
printf("\n\nfirst %d terms of Fibonacci series are:\n\n\n",n);
printf("%d ", 1);
printFibo(n);
printf("\n\n\t\t\tCoding is Fun !\n\n\n");
return 0;
}
void printFibo(int aj)
{
static long int first = 0, second = 1, sum;
if(aj > 1)
{
sum = first + second;
first = second;
second = sum;
printf("%ld ", sum);
printFibo(aj-1); // recursive call
}
else
{
// after the elements, for line break
printf("\n\n\n");
}
}
4.Program to find Sum of First N Numbers.
Program to find sum of the first n numbers using recursion, where the value of n is provided by the user.
#include<stdio.h>
// declaring the recursive function
int getSum(int);
int main()
{
printf("\n\n\t\tStudytonight - Best place to learn\n\n\n");
int n, sum;
printf("\n\nEnter the range of n: ");
scanf("%d", &n);
sum = getSum(n);
printf("\n\nThe sum of first %d numbers is %d\n", n, sum);
printf("\n\n\t\t\tCoding is Fun !\n\n\n");
return 0;
}
// function definition
int getSum(int aj)
{
/*
static variables hold their values
till the end of the program
*/
static int sum = 0;
if(aj > 0)
{
sum = sum + aj;
getSum(aj-1);
}
return sum ;
}
5.Program to find Sum of digits of a Number using Recursion.
- Program to find sum of digits of a given number using recursion.
#include<stdio.h>
#include<conio.h>
//declaring the recursive function
int sumOfDigit(int num);
void main()
{
int num, sum;
clrscr();
printf("Enter a number:\t");
scanf("%d", &num);
sum = sumOfDigit(num);
printf("The sum of digits of %d is: %d", num, sum);
getch();
}
int sumOfDigit(int num)
{
int s, a;
s = s + (num%10);
a = num/10;
if(a > 0)
{
sumOfDigit(a);
}
return s;
}
6.Program to find Palindrome using Recursion.
- Program to find whether the user input number is a palindrome or not using recursion:
#include<stdio.h>
// declaring the recursive function
int isPal(int );
/*
global declaration to use the same value
in both the functions
*/
int n;
int main()
{
printf("\n\n\t\tStudytonight - Best place to learn\n\n\n");
int palindrome;
printf("\n\nEnter a number to check for Palindrome: ");
scanf("%d", &n);
palindrome = isPal(n);
if(palindrome == 1)
printf("\n\n\n%d is palindrome\n\n", n);
else
printf("\n\n\n%d is not palindrome\n\n", n);
printf("\n\n\t\t\tCoding is Fun !\n\n\n");
return 0;
}
int isPal(int aj)
{
static int sum = 0;
if(aj != 0)
{
sum = sum *10 + aj%10;
isPal(aj/10); // recursive call same as while(n!=0) using loop
}
else if(sum == n)
return 1;
else
return 0;
}
7.Program to calculate a Number raised to the Power of N using Recursion.
- Program to calculate the result of a given number, raised to the power of n using recursion.
#include<stdio.h>
// function prototype declaration
int power(int n1, int n2);
int main()
{
printf("\n\n\t\tStudytonight - Best place to learn\n\n\n");
int base, exp;
printf("Enter base number: ");
scanf("%d", &base);
printf("\n\nEnter Power factor: ");
scanf("%d", &exp);
printf("\n\n\n\t\t\t%d^%d = %d", base, exp, power(base, exp));
printf("\n\n\t\t\tCoding is Fun !\n\n\n");
return 0;
}
int power(int b, int e)
{
if(e == 0)
return 1;
return (b*power(b, e-1));
}
8.Program to find the largest Element in an Array using Recursion.
#include<stdio.h>
#define MAX 100
int getMaxElement(int []); // takes array of int as parameter
int size;
int main()
{
printf("\n\n\t\tStudytonight - Best place to learn\n\n\n");
int arr[MAX], max, i;
printf("\n\nEnter the size of the array: ");
scanf("%d", &size);
printf("\n\nEnter %d elements\n\n", size);
for(i = 0; i < size; i++)
{
scanf("%d", &arr[i]);
}
max = getMaxElement(arr); // passing the complete array as parameter
printf("\n\nLargest element of the array is %d\n\n", max);
printf("\n\n\t\t\tCoding is Fun !\n\n\n");
return 0;
}
int getMaxElement(int a[])
{
static int i = 0, max =- 9999; // static int max=a[0] is invalid
if(i < size) // till the last element
{
if(max < a[i])
max = a[i];
i++; // to check the next element in the next iteration
getMaxElement(a); // recursive call
}
return max;
}
9.Program to find whether a Number is Prime Or Composite using Recursion.
- Prime Number: A number that is only divisible by 1 and itself.
- Composite Number: A number that is not a prime number.
Note: 1 is neither prime nor composite.
#include<stdio.h>
// declaring the recursive function
int isPrime(int, int);
int main()
{
printf("\n\n\t\tStudytonight - Best place to learn\n\n\n");
int num, prime;
printf("Enter a positive number to check if Prime: ");
scanf("%d", &num);
prime = isPrime(num, num/2);
if(prime == 1)
{
printf("\n\n%d is a prime number\n\n", num);
}
else
{
printf("\n\n%d is a Composite number\n\n", num);
}
printf("\n\n\t\t\tCoding is Fun !\n\n\n");
return 0;
}
// function definition
int isPrime(int n, int i)
{
if(i == 1)
return 1; // return statement terminates the recursive funtion
else
{
if(n%i == 0)
return 0;
else
isPrime(n, i-1); // recursive call not using return statement
}
}
10.Program to find LCM of two Numbers using Recursion.
LCM: Least Common Multiple of two numbers is the number that is a common multiple of the both the numbers.
#include<stdio.h>
int find_lcm(int, int); // function prototype declaration
int main()
{
printf("\n\n\t\tStudytonight - Best place to learn\n\n\n");
int a, b, lcm;
printf("\n\nEnter 2 integers to find LCM of:\n");
scanf("%d%d", &a, &b);
lcm = find_lcm(a,b); // function call
printf("\n\n LCM of %d and %d is: %d\n\n", a, b, lcm);
printf("\n\n\t\t\tCoding is Fun !\n\n\n");
return 0;
}
int find_lcm(int a, int b) // function definition
{
/*
static variable is initialized only once
for each function call
*/
static int temp = 1;
if(temp%a == 0 && temp%b == 0)
{
return temp;
}
else
{
temp++;
find_lcm(a,b);
return temp;
}
}
11. Program to find GCD of two Numbers using Recursion.
- Greatest Common Divisor(GCD) of two numbers is a number that divides both of them.
#include<stdio.h>
// declaring the recursive function
int find_gcd(int , int );
int main()
{
printf("\n\n\t\tStudytonight - Best place to learn\n\n\n");
int a, b, gcd;
printf("\n\nEnter two numbers to find GCD of \n");
scanf("%d%d", &a, &b);
gcd = find_gcd(a, b);
printf("\n\nGCD of %d and %d is: %d\n\n", a, b, gcd);
printf("\n\n\t\t\tCoding is Fun !\n\n\n");
return 0;
}
// defining the function
int find_gcd(int x, int y)
{
if(x > y)
find_gcd(x-y, y);
else if(y > x)
find_gcd(x, y-x);
else
return x;
}
- 12.Program to Reverse a String Using Recursion.
#include<stdio.h>
#include<conio.h>
// declaring recursive function
char* reverse(char* str);
void main()
{
int i, j, k;
char str[100];
char *rev;
printf("Enter the string:\t");
scanf("%s", str);
printf("The original string is: %s\n", str);
rev = reverse(str);
printf("The reversed string is: %s\n", rev);
getch();
}
// defining the function
char* reverse(char *str)
{
static int i = 0;
static char rev[100];
if(*str)
{
reverse(str+1);
rev[i++] = *str;
}
return rev;
}
