4. Strings Programs

Programs (Strings)

7. Program using strcpy

(Copies a string into another variable)

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

int main() {
    char source[] = "C Programming";
    char destination[50];
    
    strcpy(destination, source);
    
    printf("Source String: %s\n", source);
    printf("Destination String: %s\n", destination);
    return 0;
}

8. Program using strlen

(Finds the length of a string)

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

int main() {
    char str[50];
    printf("Enter a string: ");
    fgets(str, sizeof(str), stdin);
    
    // Removing newline added by fgets (optional but clean)
    str[strcspn(str, "\n")] = 0;
    
    int length = strlen(str);
    printf("Length of string '%s' is: %d\n", str, length);
    return 0;
}

9. Program using strcat

(Concatenates/appends one string to the end of another)

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

int main() {
    char str1[50] = "Hello ";
    char str2[] = "World!";
    
    strcat(str1, str2); // str2 is appended directly to str1
    
    printf("Concatenated String: %s\n", str1);
    return 0;
}

10. Program using strcmp

(Compares strings alphabetically)

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

int main() {
    char str1[] = "Apple";
    char str2[] = "Apple";
    char str3[] = "Banana";
    
    int result1 = strcmp(str1, str2);
    int result2 = strcmp(str1, str3);
    
    if (result1 == 0) printf("str1 and str2 are equal.\n");
    if (result2 < 0) printf("str1 comes before str3 alphabetically.\n");
    
    return 0;
}

11. Program using strchr

(Finds the first occurrence of a specific character in a string)

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

int main() {
    char str[] = "Programming in C";
    char ch = 'm';
    char *ptr;
    
    // Returns pointer to the first occurrence
    ptr = strchr(str, ch); 
    
    if (ptr != NULL) {
        printf("Character '%c' found at position: %ld\n", ch, ptr - str + 1);
    } else {
        printf("Character not found.\n");
    }
    return 0;
}

12. Program using strstr

(Finds the first occurrence of a substring in a string)

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

int main() {
    char str[] = "Learning C is amazing";
    char substr[] = "is";
    char *ptr;
    
    ptr = strstr(str, substr);
    
    if (ptr != NULL) {
        printf("Substring \"%s\" found at position: %ld\n", substr, ptr - str + 1);
    } else {
        printf("Substring not found.\n");
    }
    return 0;
}

13. Palindrome of a String (Method 1: Two-Pointer logic)

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

int main() {
    char str[50];
    int left, right, isPalindrome = 1;
    
    printf("Enter a string: ");
    scanf("%s", str); // Reading without spaces
    
    left = 0;
    right = strlen(str) - 1;
    
    while (right > left) {
        if (str[left] != str[right]) {
            isPalindrome = 0;
            break;
        }
        left++;
        right--;
    }
    
    if (isPalindrome) printf("%s is a Palindrome.\n", str);
    else printf("%s is NOT a Palindrome.\n", str);
    
    return 0;
}

20. Count Vowels, Consonants, Digits & Special Chars (<ctype.h>)

#include <stdio.h>
#include <ctype.h>

int main() {
    char line[150];
    int vowels, consonant, digit, space, special;
    vowels = consonant = digit = space = special = 0;

    printf("Enter a line of string: ");
    fgets(line, sizeof(line), stdin); // Uses string.h technically, but ctype is the focus

    for (int i = 0; line[i] != '\0'; ++i) {
        char ch = tolower(line[i]); 
        
        if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
            ++vowels;
        } else if (isalpha(ch)) { // Check if alphabet using ctype
            ++consonant;
        } else if (isdigit(ch)) { // Check if digit using ctype
            ++digit;
        } else if (isspace(ch)) { // Check if space using ctype
            ++space;
        } else {
            ++special;
        }
    }

    printf("Vowels: %d\n", vowels);
    printf("Consonants: %d\n", consonant);
    printf("Digits: %d\n", digit);
    printf("White spaces: %d\n", space);
    // Note: special count includes the newline added by fgets
    printf("Special Characters: %d\n", special - 1); 

    return 0;
}

21. Palindrome of a String (Method 2: Using standard functions and new array)

(A more manual array copy approach instead of pointers)

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

int main() {
    char original[50], reversed[50];
    int len, i, j;
    
    printf("Enter a string: ");
    scanf("%s", original);
    
    len = strlen(original);
    
    // Reverse logic building
    j = 0;
    for(i = len - 1; i >= 0; i--) {
        reversed[j] = original[i];
        j++;
    }
    reversed[len] = '\0'; // Terminate the reversed string
    
    // Compare directly
    if (strcmp(original, reversed) == 0) {
        printf("%s is a Palindrome.\n", original);
    } else {
        printf("%s is NOT a Palindrome.\n", original);
    }
    return 0;
}