✅ Day 5 Solution - DSA with C

 

✅ 1. Implement your own strlen()

#include <stdio.h>

int my_strlen(char str[]) {
    int i = 0;
    while (str[i] != '\0') {
        i++;
    }
    return i;
}

int main() {
    char str[100];
    printf("Enter a string: ");
    scanf("%s", str);
    printf("Length of string = %d\n", my_strlen(str));
    return 0;
}

---

✅ 2. Implement your own strcpy()

#include <stdio.h>

void my_strcpy(char dest[], char src[]) {
    int i = 0;
    while (src[i] != '\0') {
        dest[i] = src[i];
        i++;
    }
    dest[i] = '\0'; // Null-terminate
}

int main() {
    char src[100], dest[100];
    printf("Enter a string to copy: ");
    scanf("%s", src);

    my_strcpy(dest, src);
    printf("Copied string: %s\n", dest);
    return 0;
}

---

✅ 3. Implement your own strcmp()

#include <stdio.h>

int my_strcmp(char str1[], char str2[]) {
    int i = 0;
    while (str1[i] != '\0' && str2[i] != '\0') {
        if (str1[i] != str2[i])
            return str1[i] - str2[i];
        i++;
    }
    return str1[i] - str2[i]; // Also handles different lengths
}

int main() {
    char str1[100], str2[100];
    printf("Enter two strings:\n");
    scanf("%s %s", str1, str2);

    int result = my_strcmp(str1, str2);
    if (result == 0)
        printf("Strings are equal.\n");
    else if (result < 0)
        printf("First string is smaller.\n");
    else
        printf("First string is greater.\n");

    return 0;
}

---

✅ 4. LeetCode Problem: Valid Anagram

Two strings are anagrams if they contain the same characters in any order.

✨ Custom C Solution:

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

int isAnagram(char s[], char t[]) {
    int count[26] = {0};

    if (strlen(s) != strlen(t))
        return 0;

    for (int i = 0; s[i] != '\0'; i++) {
        count[s[i] - 'a']++;
        count[t[i] - 'a']--;
    }

    for (int i = 0; i < 26; i++) {
        if (count[i] != 0)
            return 0;
    }

    return 1;
}

int main() {
    char s[100], t[100];
    printf("Enter first string: ");
    scanf("%s", s);
    printf("Enter second string: ");
    scanf("%s", t);

    if (isAnagram(s, t))
        printf("Valid Anagram\n");
    else
        printf("Not an Anagram\n");

    return 0;
}

✅ This C code solves the Valid Anagram LeetCode problem without using libraries like sort.