In this guide we will learn best 3 ways to reverse string in C. We will take a string as input and then reverse it by library function, without library function, recursion and pointer in C.
Assume the user gives the string ‘programming‘, then we will make it ‘gnimmargorp‘ by our written C program. Let’s see the easiest solution to this reverse string program in C.
Programs to reverse string in C is given bellow;
1. Reverse string using strrev() library function
strrev() is a library function defined inside the string.h header file which can reverse the given string.
We must have to include the header file when working string function like strrev().
#include <stdio.h>
#include <string.h>
int main(){
char main_string[200];
printf("Enter a string here to reverse it : \n");
gets(main_string);
strrev(main_string);
printf("\nString after reversal is : \n%s\n", main_string);
return 0;
}Output of reverse string program
2. Reverse string without library function
In the following program we will reverse string without using library function in C. Let’s see the program bellow;
// reverse string program without library function
#include <stdio.h>
int main(){
char main_string[100], rev_string[100];
int counter = 0, start, finish;
printf("Input any string to reverse it : \n");
gets(main_string);
while(main_string[counter] != '\0'){
counter++;
}
finish = counter - 1;
for(start = 0; start < counter; start++){
rev_string[start] = main_string[finish];
finish--;
}
rev_string[start] = '\0';
printf("\nReverse string is : \n%s\n", rev_string);
return 0;
}Output of program
Input any string to reverse it :
string reversal by CP
Reverse string is :
PC yb lasrever gnirtsYou can also use function to reverse a string. Try this using function in your own.
3. Reverse string using pointer and recursion in C
// reverse string program using pointer
#include<stdio.h>
int len_finder(char *p){ // find string length by function
int i = 0;
while(*(p + i) != '\0'){
i++;
}
return i;
}
void str_rev_funct(char *strg){ // string reverse function
int strln, k;
char *s, *e, t;
strln = len_finder(strg);
s = strg;
e = strg;
for (k = 0; k < strln - 1; k++){
e++;
}
for (k = 0; k < strln / 2; k++){
t = *e;
*e = *s;
*s = t;
s++;
e--;
}
}
int main(){
char main_string[200];
printf("Enter your main string to reverse it : \n");
gets(main_string);
str_rev_funct(main_string);
printf("\nYour string after reversing is : \n%s\n", main_string);
return 0;
}Reverse string program output
Enter your main string to reverse it :
reverse string program
Your string after reversing is :
margorp gnirts esreverHope you are now clear about the ways to reverse string in C. If you have any doubt still now, don’t hesitate to comment bellow.
