C code to reverse a string without strrev() Function

To reverse any string in C language, first take the length of the string using strlen() or use For loop to get string length and than start For loop from (string length -1) to 0 and reverse string.

Note: Don't use strlen() function in For loop because the order of strlen() is O(n)  already and when we use it in For loop than order becomes O(n²).

//C program to reverse a given string without using strrev() function//

#include<stdio.h>
#include<string.h>
#include<malloc.h>

int main()
{
int i=0,length;
char *p;
p=(char*)malloc(sizeof(25));
printf("\nEnter String= ");
gets(p);

//take the length of the string
length=strlen(p);
printf("Reverse string\n");

for(i=length-1;i>=0;i--)
printf("%c",p[i]);
getch();
return 0;
}

Output of the above Program:

Reverse string in c