Reverse a String in C

This topic will discuss several ways to reverse a string in the C programming language. Reversing a string is the technique that reverses or changes the order of a given string so that the last character of the string becomes the first character of the string and so on. Furthermore, we can also check the Palindrome of the given string by reversing the original string.

For example, we enter a string “APPLE“, and then use the reverse algorithm. The reverse algorithm returns the string “ELPPA” which is completely reverse of the original string.

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 consider an example to print the reverse of a string using the strrev() function.

Program1.c

  #include   #include   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

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 consider an example to print the reverse of a string using user defined function.

Program2.c

  #include   #include     // 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

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 consider an example to print the reverse of a string using the recursion function.

Recursion function: A recursion function is a function that continuously calls the same function without using a looping statement.

Program3.c

  #include   #include     // 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

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 consider an example to print the reverse of a string using for loop in C programming language.

Program4.c

  #include   #include   #include   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 ;>

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 consider an example to print the reverse of a string using while loop in C programming language.

Program5.c

  #include   #include   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

Enter a string to be reversed: tutoraspire   The reversed of the string: TNIOPTAVAJ

Program 6: Print the reverse of a string using pointers

Let’s consider an example to print the reverse of a string using pointers in the C programming language.

Program6.c

  #include   #include     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) != ‘

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Reverse a String in C

Reverse a String in C

Different ways to find the reverse of a string in the C

Program 1: Print the reverse of a string using strrev() function

Program 2: Print the reverse of a string without using the library function

Program 3: Print the reverse of a string using the recursion function

Program 4: Print the reverse of a string using for loop

Program 5: Print the reverse of a string using while loop

Program 6: Print the reverse of a string using pointers

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