C program for operation on String

Implement following operations on the string (without library string)

1. Length 2. Palindrome 3. Comparison 4. Copy 5. Reverse      6. Substring

#include <stdio.h>

void substr(char str1[], char str2[]);

int palindrome(char str[]);

int compare(char str1[], char str2[]);

void copy(char str1[], char str2[]);

void reverse(char str[]);

int main()

{

      setbuf(stdout, NULL);

      char str1[100], str2[100];

      int result, option;

      do {

            printf("\n1.Substring Searching");

            printf("\n2.Check for Palindrome");

            printf("\n3.String Comparison");

            printf("\n4.Copy string");

            printf("\n5.Reverse String");

            printf("\n6.Quit");

            printf("\n\nEnter Your Choice:");

            scanf("%d", &option);

            switch (option)

            {

            case 1:

                  printf("\nEnter 1st string:");

                  scanf("%s",&str1);

                  printf("\nEnter 2nd string:");

                  scanf("%s",&str2);

                  substr(str1, str2);

                  break;

            case 2:

                  printf("\nEnter a String:");

                  scanf("%s",&str1);

                  result = palindrome(str1);

                  if (result == 0)

                        printf("\nNot a palindrome");

                  else

                        printf("\nIt is palindrome");

                  break;

            case 3:

                  printf("\nEnter 1st string:");

                  scanf("%s",&str1);

                  printf("\nEnter 2nd string:");

                  scanf("%s",&str2);

                  result = compare(str1, str2);

                  if (result == 0)

                        printf("\nboth are same");

                  else if (result > 0)

                        printf("\n1st>2nd");

                  else

                        printf("\n1st<2nd");

                  break;

                  case 4:

                        printf("\nEnter a String:");

                        scanf("%s",&str1);

                        copy(str2, str1);

                        printf("\nResult=%s", str2);

                        break;

                  case 5:

                        printf("\nEnter a String:");scanf("%s",&str1);

                        reverse(str1);

                        printf("\nResult=%s", str1);

                        break;

                  default:

                        printf("\nInvalid Choice:");

                        break;

            }

      } while (option != 6);

      return 0;

}

void substr(char str1[], char str2[])

{

      int i, j, lena, lenb;

      for (lena = 0; str1[lena] != '\0'; lena++);

      for (lenb = 0; str2[lenb] != '\0'; lenb++);

      for (i = 0; i <= lena - lenb + 1; i++) {

            for (j = 0; str1[i + j] == str2[j] && str2[j] != '\0'; j++);

            if (str2[j] == '\0')

                  printf("\nString found at location : %d", i + 1);

      }

}

int palindrome(char str[])

{

      int i, j;

      i = j = 0;

      while (str[j] != '\0')

            j++;

      while (i < j) {

            if (str[i] != str[j - 1])

                  return (0);

            i++;

            j--;

      }

      return (1);

}

int compare(char str1[], char str2[])

{

      int i;

      i = 0;

      while (str1[i] != '\0') {

            if (str1[i] > str2[i])

                  return (1);

            if (str1[i] < str2[i])

                  return (-1);

            i++;

      }

      return (0);

}

void copy(char str2[], char str1[])

{

      int i = 0;

      while (str1[i] != '\0') {

            str2[i] = str1[i];

            i++;

      }

      str2[i] = '\0';

}

void reverse(char str[])

{

      int i, j;

      char temp;

      i = j = 0;

      while (str[j] != '\0')

            j++;

      j--;

      while (i < j) {

            temp = str[i];

            str[i] = str[j];

            str[j] = temp;

            i++;

            j--;

      }

}

Output

1.Substring Searching

2.Check for Palindrome

3.String Comparison

4.Copy string

5.Reverse String

6.Quit

Enter Your Choice:1

Enter 1st string:madam

Enter 2nd string:am

String found at location : 4

1.Substring Searching

2.Check for Palindrome

3.String Comparison

4.Copy string

5.Reverse String

6.Quit

Enter Your Choice:2

 Enter a String:madam

A palindrome

1.Substring Searching

2.Check for Palindrome

3.String Comparison

4.Copy string

5.Reverse String

6.Quit

Enter Your Choice:3

Enter 1st string:Mam

Enter 2nd string:mam

1st<2nd

1.Substring Searching

2.Check for Palindrome

3.String Comparison

4.Copy string

5.Reverse String

6.Quit

Enter Your Choice:4

Enter a String:hello

Result=hello

1.Substring Searching

2.Check for Palindrome

3.String Comparison

4.Copy string

5.Reverse String

6.Quit

Enter Your Choice:5

Enter a String:hello

Result=olleh

1.Substring Searching

2.Check for Palindrome

3.String Comparison

4.Copy string

5.Reverse String

6.Quit

Enter Your Choice:6

Invalid Choice: