C program to reverse an array

C program to reverse an array: This program reverses the array elements. For example if a is an array of integers with three elements such that
a[0] = 1
a[1] = 2
a[2] = 3
Then on reversing the array will be
a[0] = 3
a[1] = 2
a[0] = 1
Given below is the c code to reverse an array.

C programming code

#include <stdio.h>
 
int main()
{
   int n, c, d, a[100], b[100];
 
   printf("Enter the number of elements in array\n");
   scanf("%d", &n);
 
   printf("Enter the array elements\n");
 
   for (c = 0; c < n ; c++)
      scanf("%d", &a[c]);
 
   /*
    * Copying elements into array b starting from end of array a
    */
 
   for (c = n - 1, d = 0; c >= 0; c--, d++)
      b[d] = a[c];
 
   /*
    * Copying reversed array into original.
    * Here we are modifying original array, this is optional.
    */
 
   for (c = 0; c < n; c++)
      a[c] = b[c];
 
   printf("Reverse array is\n");
 
   for (c = 0; c < n; c++)
      printf("%d\n", a[c]);
 
   return 0;
}

Download Reverse array program.
Output of program:

Reverse array by swapping (without using additional memory)

#include <stdio.h>
 
int main() {
  int array[100], n, c, t, end;
 
  scanf("%d", &n);
  end = n - 1;
 
  for (c = 0; c < n; c++) {
    scanf("%d", &array[c]);
  }
 
  for (c = 0; c < n/2; c++) {
    t          = array[c];
    array[c]   = array[end];
    array[end] = t;
 
    end--;
  }
 
  printf("Reversed array elements are:\n");
 
  for (c = 0; c < n; c++) {
    printf("%d\n", array[c]);
  }
 
  return 0;
}

C program to reverse an array using pointers

#include <stdio.h>
#include <stdlib.h>
 
void reverse_array(int*, int);
 
int main()
{
   int n, c, *pointer;
 
   scanf("%d",&n);
 
   pointer = (int*)malloc(sizeof(int)*n);
 
   if( pointer == NULL )
      exit(EXIT_FAILURE);
 
   for ( c = 0 ; c < n ; c++ )
      scanf("%d",(pointer+c));
 
   reverse_array(pointer, n);
 
   printf("Original array on reversal is\n");
 
   for ( c = 0 ; c < n ; c++ )
      printf("%d\n",*(pointer+c));
 
   free(pointer);
 
   return 0;
}
 
void reverse_array(int *pointer, int n)
{
   int *s, c, d;
 
   s = (int*)malloc(sizeof(int)*n);
 
   if( s == NULL )
      exit(EXIT_FAILURE);
 
   for ( c = n - 1, d = 0 ; c >= 0 ; c--, d++ )
      *(s+d) = *(pointer+c);
 
   for ( c = 0 ; c < n ; c++ )
      *(pointer+c) = *(s+c);
 
   free(s);
}

Array is passed to function and a new array is created and contents of passed array (in reverse order) are copied into it and finally contents of new array are copied into array passed to function.

C program for binary search

C program for binary search: This code implements binary search in c language. It can only be used for sorted arrays, but it's fast as compared to linear search. If you wish to use binary search on an array which is not sorted then you must sort it using some sorting technique say merge sort and then use binary search algorithm to find the desired element in the list. If the element to be searched is found then its position is printed.

The code below assumes that the input numbers are in ascending order.

C programming code for binary search

#include <stdio.h>
 
int main()
{
   int c, first, last, middle, n, search, array[100];
 
   printf("Enter number of elements\n");
   scanf("%d",&n);
 
   printf("Enter %d integers\n", n);
 
   for ( c = 0 ; c < n ; c++ )
      scanf("%d",&array[c]);
 
   printf("Enter value to find\n");
   scanf("%d",&search);
 
   first = 0;
   last = n - 1;
   middle = (first+last)/2;
 
   while( first <= last )
   {
      if ( array[middle] < search )
         first = middle + 1;    
      else if ( array[middle] == search ) 
      {
         printf("%d found at location %d.\n", search, middle+1);
         break;
      }
      else
         last = middle - 1;
 
      middle = (first + last)/2;
   }
   if ( first > last )
      printf("Not found! %d is not present in the list.\n", search);
 
   return 0;   
}

C program for linear search
Download Binary search program.
Output of program:

Binary search is faster than linear search but list should be sorted, hashing is faster than binary search and perform searches in constant time.

Linear search in c

Linear search in c programming: The following code implements linear search (Searching algorithm) which is used to find whether a given number is present in an array and if it is present then at what location it occurs. It is also known as sequential search. It is very simple and works as follows: We keep on comparing each element with the element to search until the desired element is found or list ends. Linear search in c language for multiple occurrences and using function.

Linear search c program

#include <stdio.h>
 
int main()
{
   int array[100], search, c, n;
 
   printf("Enter the number of elements in array\n");
   scanf("%d",&n);
 
   printf("Enter %d integer(s)\n", n);
 
   for (c = 0; c < n; c++)
      scanf("%d", &array[c]);
 
   printf("Enter the number to search\n");
   scanf("%d", &search);
 
   for (c = 0; c < n; c++)
   {
      if (array[c] == search)     /* if required element found */
      {
         printf("%d is present at location %d.\n", search, c+1);
         break;
      }
   }
   if (c == n)
      printf("%d is not present in array.\n", search);
 
   return 0;
}

Download Linear search program.
Output of program:

C program for binary search

Linear search for multiple occurrences

In the code below we will print all the locations at which required element is found and also the number of times it occur in the list.

#include <stdio.h>
 
int main()
{
   int array[100], search, c, n, count = 0;
 
   printf("Enter the number of elements in array\n");
   scanf("%d",&n);
 
   printf("Enter %d numbers\n", n);
 
   for ( c = 0 ; c < n ; c++ )
      scanf("%d",&array[c]);
 
   printf("Enter the number to search\n");
   scanf("%d",&search);
 
   for ( c = 0 ; c < n ; c++ )
   {
      if ( array[c] == search )    
      {
         printf("%d is present at location %d.\n", search, c+1);
  count++;
      }
   }
   if ( count == 0 )
      printf("%d is not present in array.\n", search);
   else
      printf("%d is present %d times in array.\n", search, count);
 
   return 0;
}

Download Linear search multiple occurrence program.
Output of code:

C program for linear search using function

#include <stdio.h>
 
int linear_search(int*, int, int);
 
int main()
{
   int array[100], search, c, n, position;
 
   printf("Enter the number of elements in array\n");
   scanf("%d",&n);
 
   printf("Enter %d numbers\n", n);
 
   for ( c = 0 ; c < n ; c++ )
      scanf("%d", &array[c]);
 
   printf("Enter the number to search\n");
   scanf("%d",&search);
 
   position = linear_search(array, n, search);
 
   if ( position == -1 )
      printf("%d is not present in array.\n", search);
   else
      printf("%d is present at location %d.\n", search, position+1);
 
   return 0;
} 
 
int linear_search(int *pointer, int n, int find)
{
   int c;
 
   for ( c = 0 ; c < n ; c++ )
   {
      if ( *(pointer+c) == find )
         return c;
   }
 
   return -1;
}

Time required to search an element using linear search algorithm depends on size of list. In best case element is present at beginning of list and in worst case element is present at the end. Time complexity of linear search is O(n).

C program to find minimum element in array

C code to find minimum or smallest element present in an array. It also prints the location or index at which minimum element occurs in array. This can also be done by using pointers (see both the codes).

C programming code

#include <stdio.h>
 
int main() 
{
    int array[100], minimum, size, c, location = 1;
 
    printf("Enter the number of elements in array\n");
    scanf("%d",&size);
 
    printf("Enter %d integers\n", size);
 
    for ( c = 0 ; c < size ; c++ )
        scanf("%d", &array[c]);
 
    minimum = array[0];
 
    for ( c = 1 ; c < size ; c++ ) 
    {
        if ( array[c] < minimum ) 
        {
           minimum = array[c];
           location = c+1;
        }
    } 
 
    printf("Minimum element is present at location %d and it's value is %d.\n", location, minimum);
    return 0;
}

Download Minimum element in array program.
Output of program:

C programming code using pointers

#include <stdio.h>
 
int main() 
{
    int array[100], *minimum, size, c, location = 1;
 
    printf("Enter the number of elements in array\n");
    scanf("%d",&size);
 
    printf("Enter %d integers\n", size);
 
    for ( c = 0 ; c < size ; c++ )
        scanf("%d", &array[c]);
 
    minimum = array;
    *minimum = *array;
 
    for ( c = 1 ; c < size ; c++ ) 
    {
        if ( *(array+c) < *minimum ) 
        {
           *minimum = *(array+c);
           location = c+1;
        }
    } 
 
    printf("Minimum element found at location %d and it's value is %d.\n", location, *minimum);
    return 0;
}

Our algorithm first assumes first element as minimum and then compare it with other elements if an element is smaller than it then it becomes the new minimum and this process is repeated till complete array is scanned.

C program to find maximum element in array

This code find maximum or largest element present in an array. It also prints the location or index at which maximum element occurs in array. This can also be done by using pointers (see both codes).

C programming code

#include <stdio.h>
 
int main()
{
  int array[100], maximum, size, c, location = 1;
 
  printf("Enter the number of elements in array\n");
  scanf("%d", &size);
 
  printf("Enter %d integers\n", size);
 
  for (c = 0; c < size; c++)
    scanf("%d", &array[c]);
 
  maximum = array[0];
 
  for (c = 1; c < size; c++)
  {
    if (array[c] > maximum)
    {
       maximum  = array[c];
       location = c+1;
    }
  }
 
  printf("Maximum element is present at location %d and it's value is %d.\n", location, maximum);
  return 0;
}

Download Maximum element in array program.
Output of program:

C programming code using pointers

#include <stdio.h>
 
int main()
{
  long array[100], *maximum, size, c, location = 1;
 
  printf("Enter the number of elements in array\n");
  scanf("%ld", &size);
 
  printf("Enter %ld integers\n", size);
 
  for ( c = 0 ; c < size ; c++ )
    scanf("%ld", &array[c]);
 
  maximum  = array;
  *maximum = *array;
 
  for (c = 1; c < size; c++)
  {
    if (*(array+c) > *maximum)
    {
       *maximum = *(array+c);
       location = c+1;
    }
  }
 
  printf("Maximum element found at location %ld and it's value is %ld.\n", location, *maximum);
  return 0;
}

The complexity of above code is O(n) as the time used depends on the size of input array or in other words time to find maximum increases linearly as array size grows.

C program to print Pascal triangle

Pascal Triangle in c: C program to print Pascal triangle which you might have studied in Binomial Theorem in Mathematics. Number of rows of Pascal triangle to print is entered by the user. First four rows of Pascal triangle are shown below :-

   1
  1 1
 1 2 1
1 3 3 1

Pascal triangle in c

#include <stdio.h>
 
long factorial(int);
 
int main()
{
   int i, n, c;
 
   printf("Enter the number of rows you wish to see in pascal triangle\n");
   scanf("%d",&n);
 
   for ( i = 0 ; i < n ; i++ )
   {
      for ( c = 0 ; c <= ( n - i - 2 ) ; c++ )
         printf(" ");
 
      for( c = 0 ; c <= i ; c++ )
         printf("%ld ",factorial(i)/(factorial(c)*factorial(i-c)));
 
      printf("\n");
   }
 
   return 0;
}
 
long factorial(int n)
{
   int c;
   long result = 1;
 
   for( c = 1 ; c <= n ; c++ )
         result = result*c;
 
   return ( result );
}

Download Pascal triangle program.
Output of program:

C program to print Floyd's triangle

C program to print Floyd's triangle:- This program prints Floyd's triangle. Number of rows of Floyd's triangle to print is entered by the user. First four rows of Floyd's triangle are as follows :-
1
2 3
4 5 6
7 8 9 10
It's clear that in Floyd's triangle nth row contains n numbers.

C programming code

#include <stdio.h>
 
int main()
{
  int n, i,  c, a = 1;
 
  printf("Enter the number of rows of Floyd's triangle to print\n");
  scanf("%d", &n);
 
  for (i = 1; i <= n; i++)
  {
    for (c = 1; c <= i; c++)
    {
      printf("%d ",a);
      a++;
    }
    printf("\n");
  }
 
  return 0;
}

Download Floyd triangle program.
Output of program: