These problems are so common that you will find in any C learning curriculum. Either in your college or in any IT institute. I have provided solutions to these problems as well. Happy learning...

1. Common Problems
Solving using C Language
Instructor:
Arghodeep Paul
Firmware Engineer at BitBible Technologies Pvt. Ltd.
Content Author: Arghodeep Paul
License: OpenSource
Date: 01 August 2021

2. IF ELSE:
1. Check whether the user entered number is positive.
#include<stdio.h>
int main(){
int number;
printf("Enter a number:");
scanf("%d",&number);
if(number>0){
printf("%d is a positive number!",number);
}
else{
printf("%d is a negative number",number);
}
return 0;
}

3. 2. Write a program to check whether a number is even
or odd.
#include<stdio.h>
int main(){
int num;
printf("Enter a number:");
scanf("%d",&num);
if(num%2==0){
printf("%d is an even number!",num);
}
else{
printf("%d is an odd number",num);
}
return 0;
}

4. FOR LOOP:
3. Write a program to display first 10 natural numbers
#include <stdio.h>
int main()
{
int i;
printf("The first 10 natural numbers are:n");
for (i=1;i<=10;i++)
{
printf("%d ",i);
}
printf("n");
return 0;
}

5. 4. Write a program to find biggest among two numbers.
#include<stdio.h>
int main()
{
int n1,n2,sum;
printf("nEnter 1st number : ");
scanf("%d",&n1);
printf("nEnter 2nd number : ");
scanf("%d",&n2);
if(n1 > n2)
printf("n1st number is greatest.");
else
printf("n2nd number is greatest.");
return 0;
}

6. WHILE LOOP:
5. Write a program to display natural numbers upto a
given range.
#include <stdio.h>
int main()
{
int num,i;
printf("Enter a number : ");
scanf("%d", &num);
i = 0;
while (i <= num)
{
printf("n%d",i);
i++;
}

7. return 0;
}
6. Write a program to display sum of first 5 natural
number.
#include <stdio.h>
int main()
{
int num, i, sum = 0;
printf("Enter a positive number : ");
scanf("%d", &num);
i = 0;
while (i <= num)
{
sum = sum + i;
i++;

8. }
printf(" n Sum of first %d natural number is : %d", num,
sum);
return 0;
}
7. Write a program to generate the following series 1 4
9 16 …. 100
#include<stdio.h>
int main()
{
int i;
for(i=1;i<=10;i++)
{
printf("n%d",i*i);
}
return 0;
}

9. 8. Write a program to find out sum of first 10 natural
numbers
int main()
{
int i, sum = 0;
i = 0;
while (i <= 10)
{
sum = sum + i;
i++;
}
printf(" n Sum of first 10 natural number is : %d", sum);

10. return 0;
}
9. Write a program to read 10 numbers and find their
sum and average
#include <stdio.h>
int main()
{
int i,n,sum=0;
float avg;
printf("Input the 10 numbers : n");
for (i=1;i<=10;i++)
{
printf("Number-%d :",i);
scanf("%d",&n);
sum +=n;
}
avg=sum/10.0;
printf("The sum of 10 no is : %dnThe Average
is : %fn",sum,avg);
return 0;

11. }
10. Find cube of the number upto a given integer
#include <stdio.h>
int main()
{
int i,ctr;
printf("Input number of terms : ");
scanf("%d", &ctr);
for(i=1;i<=ctr;i++)
{
printf("Number is : %d and cube of the %d is :%d n",i,i,
(i*i*i));

12. }
return 0;
}
11. Compute multiplication table of a given integer
#include <stdio.h>
int main()
{
int j,n;
printf("Input the number (Table to be calculated) : ");
scanf("%d",&n);
printf("nn");
for(j=1;j<=10;j++)
{
printf("%d X %d = %d n",n,j,n*j);
}
return 9;
}

13. 12. Display n number of multiplication table vertically
#include <stdio.h>
int main()
{
int j,i,n;
printf("Input upto the table number starting from 1 : ");
scanf("%d",&n);
printf("Multiplication table from 1 to %d n",n);
for(i=1;i<=10;i++)
{
for(j=1;j<=n;j++)
{
if (j<=n-1)
printf("%dx%d = %d, ",j,i,i*j);
else

14. printf("%dx%d = %d",j,i,i*j);
}
printf("n");
}
return 0;
}
13. Check whether the entered year is leap year or not.
#include <stdio.h>
int main() {
int year;
printf("Enter a year: ");
scanf("%d", &year);

15. // leap year if perfectly divisible by 400
if (year % 400 == 0) {
printf("%d is a leap year.", year);
}
// not a leap year if divisible by 100
// but not divisible by 400
else if (year % 100 == 0) {
printf("%d is not a leap year.", year);
}
// leap year if not divisible by 100
// but divisible by 4
else if (year % 4 == 0) {
printf("%d is a leap year.", year);
}
// all other years are not leap years
else {
printf("%d is not a leap year.", year);
}
return 0;
}

16. 14. Find out the sum of odd numbers upto a given
range.
#include <stdio.h>
int main()
{
int i, n, sum=0;
/* Input range to find sum of odd numbers */
printf("Enter upper limit: ");
scanf("%d", &n);
/* Find the sum of all odd number */
for(i=1; i<=n; i+=2)
{
sum += i;
}
printf("Sum of odd numbers = %d", sum);
return 0;
}

17. 15. Write a program to print the series 0,1,3,6,10 upto
N
#include<stdio.h>
int main()
{
int i,j=1,k=1,n;
printf("nEnter number of terms:");
scanf("%d",&n);
printf("n");
printf(“%dt”,0);
for(i=0;i<n;i++)
{
printf("%dt",k);
j=j+1;
k=k+j;
}
return 0;
}

18. 16. Find factorial of a user given number
#include <stdio.h>
int main()
{
int c, n, f = 1;
printf("Enter a number to calculate its factorial:");
scanf("%d", &n);
for (c = 1; c <= n; c++)
f = f * c;
printf("Factorial of %d = %dn", n, f);
return 0;
}

19. PATTERN:
17. Write a program to generate a pyramid pattern.
#include <stdio.h>
int main() {
int i, space, rows, k = 0;
printf("Enter the number of rows: ");
scanf("%d", &rows);
for (i = 1; i <= rows; ++i, k = 0) {
for (space = 1; space <= rows - i; ++space)
{printf(" ");
}
while (k != 2 * i - 1) {
printf("* ");
++k;
}
printf("n");
}
return 0;
}

20. 18. Write a program to generate a ring angle like
pattern with numbers.
#include <stdio.h>
int main() {
int i, j, rows;
printf("Enter the number of rows: ");
scanf("%d", &rows);
for (i = 1; i <= rows; ++i)
{for (j = 1; j <= i; ++j) {
printf("%d ", j);
}
printf("n");
}
return 0;
}

21. FUNCTION:
19. Create a user defined function addition() to add
two user input numbers.
#include<stdio.h>
int main() {
int num1, num2, res;
printf("nEnter the two numbers : ");
scanf("%d %d", &num1, &num2);
//Call Function Sum With Two Parameters
res = addition(num1, num2);
printf("nAddition of two number is : %d",res);
return (0);
}

22. int addition(int num1, int num2)
{int num3;
num3 = num1 + num2;
return (num3);
}
20. Find maximum of two numbers entered by user
using function.
#include <stdio.h>
int max(int num1, int num2);
int main()
{
int num1, num2, maximum;
printf("Enter any two numbers: ");
scanf("%d%d", &num1, &num2);
maximum = max(num1, num2);
printf("nMaximum = %dn", maximum);
return 0;
}
int max(int num1, int num2)

23. {
return (num1 > num2 ) ? num1 : num2;
}
21. Find out average of two numbers using function.
#include <stdio.h>
float average(int x, int
y){return (float)(x + y)/2;
}
int main(){
int number1, number2;
float avg;
printf("Enter the first number: ");
scanf("%d",&number1);
printf("Enter the second number: ");
scanf("%d",&number2);
avg = average(number1, number2);
printf("The Average of %d and %d
is: %.2f",number1,number2,avg);
return 0;
}

24. ARRAY:
22. Write a program to store elements in an array and
print.
#include <stdio.h>
void main()
{
int arr[10];
int i;
printf("nnRead and Print elements of an array:n");
printf(" n");
printf("Input 10 elements in the array :n");
for(i=0; i<10; i++)
{
printf("element - %d : ",i);
scanf("%d", &arr[i]);
}

25. printf("nElements in array are: ");
for(i=0; i<10; i++)
{
printf("%d ", arr[i]);
}
printf("n");
}

26. 23. Store elements upto n in an array and show in
reversed order.
#include <stdio.h>
#define MAX_SIZE 100
int main()
{
int arr[MAX_SIZE];
int size, i;
printf("Enter size of the array: ");
scanf("%d", &size);
printf("Enter elements in array: ");
for(i=0; i<size; i++)
{
scanf("%d", &arr[i]);
}
printf("nArray in reverse order: ");
for(i = size-1; i>=0; i--)
{
printf("%dt", arr[i]);
}
return 0;
}

27. 24. Find the sum of all elements in an array.
#include <stdio.h>
void main()
{
int a[100];
int i, n, sum=0;
printf("nnFind sum of all elements of array:n");
printf(" n");
printf("Input the number of elements to be stored in the
array :");
scanf("%d",&n);
printf("Input %d elements in the array :n",n);

28. for(i=0;i<n;i++)
{
printf("element - %d : ",i);
scanf("%d",&a[i]);
}
for(i=0; i<n; i++)
{
sum += a[i];
}
printf("Sum of all elements stored in the array is : %dnn",
sum);
}

29. 25. Find out the smallest element in an array.
#include <stdio.h>
int main()
{
int arr[] = {25, 11, 7, 75, 56};
int length = sizeof(arr)/sizeof(arr[0]);
int min = arr[0];
for (int i = 0; i < length; i++) {
//Compare elements of array with min
if(arr[i] < min)
min = arr[i];
}
printf("Smallest element present in given array: %dn", min);
return 0;
}

30. Thank You….. :)
Sincerely…
Arghodeep Paul