Different ways to find the reverse of a string in the C
Following are the various ways to find the reverse of a string in the C programming language:
- Reverse a string using the strrev function
- Reverse a string without using the library function
- Reverse a string using the recursion function
- Reverse a string using for loop
- Reverse a string using while loop
- Reverse a string using pointers
- Reverse a string to check for Palindrome
Program 1: Print the reverse of a string using strrev function
Let's explore an illustration demonstrating the reversal of a string by utilizing the strrev function.
Program1.c
Example
#include <stdio.h>
#include <string.h>
int main()
{
char str[40]; // declare the size of character string
printf (" \n Enter a string to be reversed: ");
scanf ("%s", str);
// use strrev() function to reverse a string
printf (" \n After the reverse of a string: %s ", strrev(str));
return 0;
}
Output
Output
Enter a string to be reversed: AMBULANCE
After the reverse of a string: ECNALUBMA
Program 2: Print the reverse of a string without using the library function
Let's explore an illustration demonstrating how to output the inverse of a string by employing a custom function.
Program2.c
Example
#include <stdio.h>
#include <string.h>
// function definition of the revstr()
void revstr(char *str1)
{
// declare variable
int i, len, temp;
len = strlen(str1); // use strlen() to get the length of str string
// use for loop to iterate the string
for (i = 0; i < len/2; i++)
{
// temp variable use to temporary hold the string
temp = str1[i];
str1[i] = str1[len - i - 1];
str1[len - i - 1] = temp;
}
}
int main()
{
char str[50]; // size of char string
printf (" Enter the string: ");
gets(str); // use gets() function to take string
printf (" \n Before reversing the string: %s \n", str);
// call revstr() function
revstr(str);
printf (" After reversing the string: %s", str);
}
Output
Output
Enter the string: Welcome Friends
Before reversing the string: Welcome Friends
After reversing the string: sdneirF emocleW
Program 3: Print the reverse of a string using the recursion function
Let's explore a scenario where we demonstrate how to output the reverse of a string by employing a recursive function.
A recursive function is a function that repeatedly invokes itself without the need for a loop construct.
Program3.c
Example
#include <stdio.h>
#include <string.h>
// use recursion function
void revstr(char *str1)
{
// declare static variable
static int i, len, temp;
len = strlen(str1); // use strlen() to get the length of str string
if (i < len/2){
// temp variable use to temporary hold the string
temp = str1[i];
str1[i] = str1[len - i - 1];
str1[len - i - 1] = temp;
i++;
revstr(str1); // recusively calls the revstr() function
}
}
int main()
{
char str1[50]; // size of char string
printf (" Enter the string: ");
gets(str1); // use gets() function to take string
printf (" \n Before reversing the string: %s \n", str1);
// call revstr() function
revstr(str1);
printf (" After reversing the string: %s", str1);
}
Output
Output
Enter the string: LIFE INSURANCE
Before reversing the string: LIFE INSURANCE
After reversing the string: ECNARUSNI EFIL
Program 4: Print the reverse of a string using for loop
Let's explore an illustration demonstrating how to display the inverted form of a string by employing a for loop in the C programming language.
Program4.c
Example
#include <stdio.h>
#include <conio.h>
#include <string.h>
void main()
{
char str[50], temp; // define the size of str[] array
int i, left, right, len;
printf (" \n Display a reverse string in the C: \n");
printf (" ----------------------- ");
printf (" \n Enter a string to reverse order: ");
scanf( "%s", &str);
len = strlen(str); // get the length of the string
left = 0; // set left index at 0
right = len - 1; // set right index len - 1
// use for loop to store the reverse string
for (i = left; i <right; i++)
{
temp = str[i];
str[i] = str[right];
str[right] = temp;
right--;
}
printf (" The reverse of the original string is: %s ", str);
getch();
}
Output
Output
Display a reverse string in the C:
-----------------------
Enter a string to reverse order: APPLE
The reverse of the original string is: ELPPA
Program 5: Print the reverse of a string using while loop
Let's explore an illustration demonstrating how to display the inverse of a string utilizing a while loop in the C programming language.
Program5.c
Example
#include <stdio.h>
#include <string.h>
int main()
{
char str1[50], temp; // declare and initialize the size of string array.
int i = 0, j =0;
printf (" Enter a string to be reversed: ");
scanf( "%s", str1);
j = strlen (str1) - 1; // get the length of the string
// use while loop to define the condition
while ( i < j)
{
// use temp variable to store the characters of str1
temp = str1[j];
str1[j] = str1[i];
str1[i] = temp;
i++; // i incremented by 1
j--; // j is decremented by 1
}
printf (" The reversed of the string: %s", str1);
return 0;
}
Output
Output
Enter a string to be reversed: LOGIC PRACTICE
The reversed of the string: TNIOPTAVAJ
Program 6: Print the reverse of a string using pointers
Let's explore a demonstration of reversing a string by utilizing pointers in the C programming language.
Program6.c
Example
#include <stdio.h>
#include <string.h>
int str_len( char *st);
void revstr( char *st);
int main()
{
char st[50];
printf (" Enter a string to be reversed: ");
scanf( "%s", st);
revstr(st);
printf (" The reverse string is: %s", st);
return 0;
}
void revstr (char *st)
{
int len, i;
char *start, *end, temp;
len = str_len (st);
start = st;
end = st;
for (i = 0; i < len - 1; i++)
end++;
for (i = 0; i < len/2; i++)
{
temp = *end;
*end = *start;
*start = temp;
start++;
end--;
}
}
int str_len (char *ptr)
{
int i = 0;
while ( *(ptr + i) != '\0')
i++;
return i;
}
Output
Output
Enter a string to be reversed: LOGIC PRACTICE
The reverse string is: TNIOPTAVAJ
Program 7: Program to check whether the reverse string is a Palindrome
Consider a script to verify if a provided string is a palindrome in the C programming language.
Program7.c
Example
#include <stdio.h>
#include <string.h>
int main ()
{
// declare variables
char str1[30];
int i, len, flag = 0;
printf (" Enter a string: ");
scanf ("%s", str1);
len = strlen( str1 ); // get the string length
for ( i = 0; i < len; i++)
{
// str1[i] is not equal to str1[len-i-1]
if (str1[i] != str1[len - i - 1])
{
flag = 1;
break; // exit from if statement
}
}
if (flag)
{
printf (" %s is not a palindrome string", str1);
}
else
{
printf (" %s is a palindrome", str1);
}
return 0;
}
Output
Output
Enter a string: madam
madam is a palindrome string.