Lab: Basic Strings Operation

1. Program to Input a String and Print Its Length

#include <stdio.h>

int main() {
    char str[100];  
    int length = 0; 

    // Input the string
    printf("Enter a string: ");
    scanf("%s", str);  

    // Calculate length of the string
    while (str[length] != '\0') {
        length++;
    }

    // Print the length
    printf("The length of the string is: %d\n", length);

    return 0;
}

2. Program to Concatenate Two Strings Without Using strcat()

#include <stdio.h>

int main() {
    char str1[100], str2[100];  
    int i = 0, j = 0;

    // Input two strings
    printf("Enter first string: ");
    scanf("%s", str1);  
    printf("Enter second string: ");
    scanf("%s", str2);  

    // Find the end of the first string
    while (str1[i] != '\0') {
        i++;
    }

    // Append the second string to the first string
    while (str2[j] != '\0') {
        str1[i] = str2[j];
        i++;
        j++;
    }
    str1[i] = '\0';  // Null-terminate the concatenated string

    // Print the concatenated string
    printf("Concatenated string: %s\n", str1);

    return 0;
}

3. Program to Compare Two Strings Without Using strcmp()

#include <stdio.h>

int main() {
    char str1[100], str2[100];  
    int i = 0, flag = 0;

    // Input two strings
    printf("Enter first string: ");
    scanf("%s", str1);  // Read first string
    printf("Enter second string: ");
    scanf("%s", str2);  // Read second string

    // Compare the strings character by character
    while (str1[i] != '\0' && str2[i] != '\0') {
        if (str1[i] != str2[i]) {
            flag = 1;  // Strings are not equal
            break;
        }
        i++;
    }

    // Check if the strings are equal
    if (flag == 0 && str1[i] == '\0' && str2[i] == '\0') {
        printf("The strings are equal.\n");
    } else {
        printf("The strings are not equal.\n");
    }

    return 0;
}

4. Program to Copy One String Into Another Without Using strcpy()

#include <stdio.h>

int main() {
    char src[100], dest[100];  

    // Input the source string
    printf("Enter a string: ");
    scanf("%s", src);  

    // Copy source string into destination string
    while (src[i] != '\0') {
        dest[i] = src[i];
        i++;
    }
    dest[i] = '\0';  

    // Print the copied string
    printf("Copied string: %s\n", dest);

    return 0;
}

5. Program to Reverse a String Without Using strrev()

#include <stdio.h>

int main() {
    char str[100];  
    int i = 0, j = 0;
    char temp;

    // Input the string
    printf("Enter a string: ");
    scanf("%s", str); 

    // Find the length of the string
    while (str[j] != '\0') {
        j++;
    }
    j--;  // Set j to the last character of the string (before null terminator)

    // Reverse the string using two-pointer technique
    while (i < j) {
        temp = str[i];
        str[i] = str[j];
        str[j] = temp;
        i++;
        j--;
    }

    // Print the reversed string
    printf("Reversed string: %s\n", str);

    return 0;
}