Strings in C

#include <stdio.h>

int main() {
    // Method 1: String literal
    char str1[] = "Hello";
    
    // Method 2: Character array
    char str2[] = {'H', 'e', 'l', 'l', 'o', '\0'};
    
    // Method 3: Fixed size
    char str3[50] = "Hello";
    
    // Print strings
    printf("str1: %s\n", str1);
    printf("str2: %s\n", str2);
    
    // Access individual characters
    printf("First char: %c\n", str1[0]);
    printf("Last char: %c\n", str1[4]);
    
    // Modify string
    str1[0] = 'h';
    printf("Modified: %s\n", str1);
    
    return 0;
}

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

int main() {
    char str1[50] = "Hello";
    char str2[50] = "World";
    char str3[50];
    
    // strlen - Get length
    printf("Length of str1: %zu\n", strlen(str1));
    
    // strcpy - Copy string
    strcpy(str3, str1);
    printf("After strcpy: %s\n", str3);
    
    // strcat - Concatenate
    strcat(str1, " ");
    strcat(str1, str2);
    printf("After strcat: %s\n", str1);
    
    // strcmp - Compare
    if (strcmp(str1, str2) == 0)
        printf("Strings are equal\n");
    else
        printf("Strings are different\n");
    
    // strchr - Find character
    char *ptr = strchr(str1, 'W');
    if (ptr != NULL)
        printf("Found 'W' at position: %ld\n", ptr - str1);
    
    // strstr - Find substring
    ptr = strstr(str1, "World");
    if (ptr != NULL)
        printf("Found 'World' at position: %ld\n", ptr - str1);
    
    return 0;
}

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

// Reverse string
void reverse(char str[]) {
    int len = 0;
    while (str[len] != '\0') len++;
    
    for (int i = 0; i < len / 2; i++) {
        char temp = str[i];
        str[i] = str[len - 1 - i];
        str[len - 1 - i] = temp;
    }
}

// Check palindrome
int isPalindrome(char str[]) {
    int len = 0;
    while (str[len] != '\0') len++;
    
    for (int i = 0; i < len / 2; i++) {
        if (str[i] != str[len - 1 - i])
            return 0;
    }
    return 1;
}

// Convert to uppercase
void toUpper(char str[]) {
    for (int i = 0; str[i] != '\0'; i++) {
        if (str[i] >= 'a' && str[i] <= 'z')
            str[i] = str[i] - 32;
    }
}

// Count vowels
int countVowels(char str[]) {
    int count = 0;
    for (int i = 0; str[i] != '\0'; i++) {
        char c = tolower(str[i]);
        if (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u')
            count++;
    }
    return count;
}

int main() {
    char str[100];
    
    printf("Enter a string: ");
    scanf(" %[^\n]", str);
    
    printf("Original: %s\n", str);
    
    printf("Vowels: %d\n", countVowels(str));
    
    if (isPalindrome(str))
        printf("Palindrome: Yes\n");
    else
        printf("Palindrome: No\n");
    
    toUpper(str);
    printf("Uppercase: %s\n", str);
    
    return 0;
}

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

int main() {
    // Array of strings
    char names[5][20] = {
        "Alice",
        "Bob",
        "Charlie",
        "David",
        "Eve"
    };
    
    // Print all names
    printf("Names:\n");
    for (int i = 0; i < 5; i++) {
        printf("%d. %s\n", i + 1, names[i]);
    }
    
    // Sort names
    char temp[20];
    for (int i = 0; i < 4; i++) {
        for (int j = i + 1; j < 5; j++) {
            if (strcmp(names[i], names[j]) > 0) {
                strcpy(temp, names[i]);
                strcpy(names[i], names[j]);
                strcpy(names[j], temp);
            }
        }
    }
    
    printf("\nSorted names:\n");
    for (int i = 0; i < 5; i++) {
        printf("%d. %s\n", i + 1, names[i]);
    }
    
    return 0;
}