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C program to reverse a string without using library function

In this program, we will learn how to reverse a string without using library function?

Here, we are declaring two strings (character arrays), first string will store the input string and other will store the reversed string.

C program to reverse a string without using library function

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

int main() {
  char str[100], revStr[100];
  int i, j;

  printf("Enter a string: ");
  scanf("%[^\n]s", str);  // read string with spaces

  /*copy characters from last index of str and
store it from starting in revStr*/
  j = 0;
  for (i = (strlen(str) - 1); i >= 0; i--) revStr[j++] = str[i];

  // assign NULL in the revStr
  revStr[j] = '\0';

  printf("\nOriginal String is: %s", str);
  printf("\nReversed String is: %s", revStr);

  return 0;
}

Output

Enter a string: This is a test string
Original String is: This is a test string
Reversed String is: gnirts tset a si sihT

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