TOP 15 IMPORTANT PROGRAMS FOR INTERVIEWS WITH SOLUTION

1. #include<stdio.h>
2. int main(){
3. int n,i,m=0,flag=0;
4. printf(“Enter the number to check prime:”);
5. scanf(“%d”,&n);
6. m=n/2;
7. for(i=2;i<=m;i++)
8. {
9. if(n%i==0)
10. {
11. printf(“Number is not prime”);
12. flag=1;
13. break;
14. }
15. }
16. if(flag==0)
17. printf(“Number is prime”);
18. return 0;
19.  }

1. #include<stdio.h>  
2. int main()
3. {
4.  int n1=0,n2=1,n3,i,number;
5.  printf(“Enter the number of elements:”);
6.  scanf(“%d”,&number);
7.  printf(“\n%d %d”,n1,n2);//printing 0 and 1  
8.  for(i=2;i<number;++i)//loop starts from 2 because 0 and 1 are already printed  
9.  {
10.   n3=n1+n2;
11.   printf(” %d”,n3);
12.   n1=n2;
13.   n2=n3;
14.  }
15.   return 0;
16.  }

The above program is Fibonacci Series without Recursion

1. #include<stdio.h>  
2. void printFibonacci(int n){
3.     static int n1=0,n2=1,n3;
4.     if(n>0){
5.          n3 = n1 + n2;
6.          n1 = n2;
7.          n2 = n3;
8.          printf(“%d “,n3);
9.          printFibonacci(n-1);
10.     }
11. }
12. int main(){
13.     int n;
14.     printf(“Enter the number of elements: “);
15.     scanf(“%d”,&n);
16.     printf(“Fibonacci Series: “);
17.     printf(“%d %d “,0,1);
18.     printFibonacci(n-2);//n-2 because 2 numbers are already printed  
19.   return 0;
20.  }    ‘

The above Program is Fibonacci Series with Recursion

3.Factorial Number Program

Factorial: Factorial is represented as “5!” that means, 5*4*3*2*1

1. #include<stdio.h>
2. int main()
3. {
4.  int i,fact=1,number;
5.  printf(“Enter a number: “);
6.   scanf(“%d”,&number);
7.     for(i=1;i<=number;i++){
8.       fact=fact*i;
9.   }
10.   printf(“Factorial of %d is: %d”,number,fact);
11. return 0;
12. }

4. Pattern Program:

Output:

*

*         *

*      *        *

5. Sum of Digits in a Program:

1. #include<stdio.h>
2.  int main()
3. {
4. int n,sum=0,m;
5. printf(“Enter a number:”);
6. scanf(“%d”,&n);
7. while(n>0)
8. {
9. m=n%10;
10. sum=sum+m;
11. n=n/10;
12. }
13. printf(“Sum is=%d”,sum);
14. return 0;
15. }

Output:

Enter a number:654

Sum is=15

Enter a number:123

Sum is=6

6. Given Number is Palindrome Number or not:

Palindrome: Palindrome is a number that is same even after reverse.

Example: 121, 34543

1. #include<stdio.h>
2. int main()
3. {
4. int n,r,sum=0,temp;
5. printf(“enter the number=”);
6. scanf(“%d”,&n);
7. temp=n;
8. while(n>0)
9. {
10. r=n%10;
11. sum=(sum*10)+r;
12. n=n/10;
13. }
14. if(temp==sum)
15. printf(“palindrome number “);
16. else
17. printf(“not palindrome”);
18. return 0;
19. }

Output: 

Given Number: 151

The Number is Palindrome

7. Given Number is Leap Year is not?

#include <stdio.h>

int main()
{    
    int year;      
    printf("Enter a year to check if it is a leap year\n");
    scanf("%d", &year);
          
    if ( year%400 == 0)      
    printf("%d is a leap year.\n", year);  
        
    else if ( year%100 == 0)      
    printf("%d is not a leap year.\n", year); 
         
    else if ( year%4 == 0 )      
    printf("%d is a leap year.\n", year);
    
    else      
    printf("%d is not a leap year.\n", year);      
    
    return 0;    
}

Output of program:

Enter a year to check it is a leap year or not

2012

2012 is not a leap year

8. Given Number is Armstrong Number or Not?

Armstrong Number: It is a number that is sum of cubes of its number.

For example take a number: 371

Logic:

1. 371 = (3*3*3)+(7*7*7)+(1*1*1)
2. where:
3. (3*3*3)=27
4. (7*7*7)=343
5. (1*1*1)=1
6. So:
7. 27+343+1=371

Program:

1. #include<stdio.h>
2.  int main()
3. {
4. int n,r,sum=0,temp;
5. printf(“enter the number=”);
6. scanf(“%d”,&n);
7. temp=n;
8. while(n>0)
9. {
10. r=n%10;
11. sum=sum+(r*r*r);
12. n=n/10;
13. }
14. if(temp==sum)
15. printf(“armstrong  number “);
16. else
17. printf(“not armstrong number”);
18. return 0;
19. }

9. Given Number is Strong or Not:

Strong Number: If sum of the factorial of the individual digits is equal to the number.

Program:

1. #include <stdio.h>
2. int main()
3. {
4.     int n;
5.     int sum=0;
6.     printf(“Enter a number”);
7.     scanf(“%d”,&n);
8.     int k=n;
9.     int r;
10.     while(k!=0)
11.     {
12.         r=k%10;
13.         int f=fact(r);
14.         k=k/10;
15.         sum=sum+f;
16.     }
17.     if(sum==n)
18.     {
19.         printf(“\nNumber is a strong”);
20.     }
21.     else
22.     {
23.         printf(“\nNumber is not a strong”);
24.     }
25.     return 0;
26. }
27. int fact(int r)
28. {
29.     int mul=1;
30.     for(int i=1;i<=r;i++)
31.     {
32.         mul=mul*i;
33.     }
34.     return mul;
36. }

10. Given Number is Perfect Number or not?

Perfect Number: 

1. #include<stdio.h>
2. #include<conio.h>
3. void main()
4. {
5. int i = 1, num, Sum = 0;
6. printf(” Enter any number to check Perfect Number \n”);
7. scanf(“%d”, &num);
9. while(i < num )
10.                      {
11.                                if(num % i == 0)
12.                                Sum = Sum + i;
13.                                i++;
14.                      }
15.            if(Sum == num)
16.                   printf(“\n %d is Perfect Number”, num);
17.            else
18.            printf(“\n %d is not a Perfect Number”, num);
19. getch();
20. }

11. Swapping of 2 numbers without using the 3rd Number:

1. #include<stdio.h>
2.  int main()
3. {
4. int a=10, b=20;
5. printf(“Before swap a=%d b=%d”,a,b);
6. a=a+b;//a=30 (10+20)  
7. b=a-b;//b=10 (30-20)  
8. a=a-b;//a=20 (30-10)  
9. printf(“\nAfter swap a=%d b=%d”,a,b);
10. return 0;
11. }

12. Harshad Number:

If a number is divisible by the sum of its digits then it will be known as a Harshad Number.

For example:

156 is divisible by the sum (12) of its digits (1, 5, 6 ).

1. #include <stdio.h>  
3. int main()
4. {
5.     int num = 156;
6.     int rem = 0, sum = 0, n;
8.     //Make a copy of num and store it in variable n  
9.     n = num;
11.     //Calculates sum of digits  
12.     while(num > 0){
13.         rem = num%10;
14.         sum = sum + rem;
15.         num = num/10;
16.     }
18.     //Checks whether number is divisible by sum of digits  
19.     if(n%sum == 0)
20.         printf(“%d is a harshad number”, n);
21.     else
22.         printf(“%d is not a harshad number”, n);
24.     return 0;
25. }

13. Program to check whether a given number is EVEN or ODD

#include <stdio.h>
int main() {
    int num;
    printf("Enter an integer: ");
    scanf("%d", &num);

    // true if num is perfectly divisible by 2
    if(num % 2 == 0)
        printf("%d is even.", num);
    else
        printf("%d is odd.", num);
    
    return 0;
}

 14. Reversing of Numbers:

1. #include<stdio.h>
2.  int main()
3. {
4. int n, reverse=0, rem;
5. printf(“Enter a number: “);
6.   scanf(“%d”, &n);
7.   while(n!=0)
8.   {
9.      rem=n%10;
10.      reverse=reverse*10+rem;
11.      n/=10;
12.   }
13.   printf(“Reversed Number: %d”,reverse);
14. return 0;
15. }

15. Program to convert Decimal to Binary:

1. #include<stdio.h>  
2. #include<stdlib.h>
3. int main(){
4. int a[10],n,i;
5. system (“cls”);
6. printf(“Enter the number to convert: “);
7. scanf(“%d”,&n);
8. for(i=0;n>0;i++)
9. {
10. a[i]=n%2;
11. n=n/2;
12. }
13. printf(“\nBinary of Given Number is=”);
14. for(i=i-1;i>=0;i–)
15. {
16. printf(“%d”,a[i]);
17. }
18. return 0;
19. }

Output:

Enter the number to convert: 5

Binary of Given Number is=101

This program can be written in C/JAVA/PYTHON. We have provided

in C Language