AI Coding & CSE Fundamentals

💡 Approach Step 1: Open a Text Editor: Use a basic text editor (like Notepad on Windows, TextEdit on macOS, or gedit/nano on Linux) to create a new file. Step 2: Write the C Code: Type the following C code into the text editor:

#include <stdio.h>

int main() {
  printf("Hello, World!\n");
  return 0;
}

Step 3: Save the File: Save the file with a .c extension, for example, hello.c. Choose a location where you can easily find it (e.g., your desktop). Step 4: Open a Command Prompt/Terminal: Open the command prompt (Windows) or terminal (macOS/Linux). Step 5: Navigate to the Directory: Use the cd command to navigate to the directory where you saved the hello.c file. For example, if you saved it on your desktop, you might use cd Desktop (Windows) or cd ~/Desktop (macOS/Linux). Step 6: Compile the Code: Use a C compiler (like GCC) to compile the code. Type the following command and press Enter: gcc hello.c -o hello (This creates an executable file named "hello"). If you are on Windows and GCC is not recognized, you might need to configure your system's PATH environment variable to include the directory where GCC is installed. Step 7: Run the Executable: Execute the compiled program. On Windows, type hello.exe and press Enter. On macOS/Linux, type ./hello and press Enter. ───────────────────────────── Have you Understood? Drop a reaction: ❤️ Understood | 👎 Not Understood

📝 Program to compile and run your first 'Hello, World!' on the console. Write a C program that prints the message "Hello, World!" to the console. This program serves as an introductory exercise to ensure your C development environment is properly set up and you can successfully compile and execute a basic C program.

📚 1. Absolute Fundamentals: Setting Up & Basic Interaction

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Count Words in a Sentence

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

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

 printf("Enter a sentence: ");
 fgets(str, sizeof(str), stdin);

 for (i = 0; str[i] != '\0'; i++) {
 if (str[i] == ' ') {
 count++;
 }
 }
 if (strlen(str) > 1) {
 count++;
 }

 printf("Number of words: %d\n", count);
 return 0;
}

Pangram Checker

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

int isPangram(const char *str) {
 int alphabet[26] = {0};
 int index;
 int i;
 for (i = 0; str[i] != '\0'; i++) {
 if (isalpha(str[i])) {
  index = tolower(str[i]) - 'a';
  alphabet[index] = 1;
 }
 }
 for (i = 0; i < 26; i++) {
 if (alphabet[i] == 0) {
  return 0;
 }
 }
 return 1;
}

int main() {
 char str[100];
 fgets(str, sizeof(str), stdin);
 str[strcspn(str, "\n")] = 0;
 if (isPangram(str)) {
 printf("Pangram\n");
 } else {
 printf("Not a Pangram\n");
 }
 return 0;
}

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Capitalize First Letter of Words in a Sentence

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

void capitalize(char str[]) {
    int i = 0;
    if (str[i] != '\0') {
        str[i] = toupper(str[i]);
        i++;
    }
    while (str[i] != '\0') {
        if (str[i-1] == ' ') {
            str[i] = toupper(str[i]);
        }
        i++;
    }
}

int main() {
    char sentence[100];
    printf("Enter a sentence: ");
    fgets(sentence, sizeof(sentence), stdin);
    sentence[strcspn(sentence, "\n")] = 0;
    capitalize(sentence);
    printf("Capitalized sentence: %s\n", sentence);
    return 0;
}

Longest Word in a Sentence

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

int main() {
  char sentence[100];
  char word[50];
  char longest[50] = "";
  int i, j, len, maxLen = 0;

  printf("Enter a sentence: ");
  fgets(sentence, sizeof(sentence), stdin);
  sentence[strcspn(sentence, "\n")] = 0;

  len = strlen(sentence);
  j = 0;
  for (i = 0; i <= len; i++) {
    if (sentence[i] == ' ' || sentence[i] == '\0') {
      word[j] = '\0';
      if (strlen(word) > maxLen) {
        maxLen = strlen(word);
        strcpy(longest, word);
      }
      j = 0;
    } else {
      word[j++] = sentence[i];
    }
  }

  printf("Longest word: %s\n", longest);
  return 0;
}

Remove Repeated Characters from a String

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

int main() {
 char str[100], result[100];
 int i, j, k = 0, len;
 int found;

 printf("Enter a string: ");
 fgets(str, sizeof(str), stdin);
 str[strcspn(str, "\n")] = 0;

 len = strlen(str);

 for (i = 0; i < len; i++) {
 found = 0;
 for (j = 0; j < k; j++) {
 if (str[i] == result[j]) {
 found = 1;
 break;
 }
 }
 if (!found) {
 result[k++] = str[i];
 }
 }
 result[k] = '\0';

 printf("String with unique characters: %s\n", result);
 return 0;
}

String Contains Only Digits

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

int main() {
  char str[100];
  int i, len, flag = 1;

  scanf("%s", str);
  len = strlen(str);

  for (i = 0; i < len; i++) {
    if (!isdigit(str[i])) {
      flag = 0;
      break;
    }
  }

  if (flag == 1) {
    printf("Yes");
  } else {
    printf("No");
  }
  return 0;
}

Find Most Frequent Character in a String

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

int main() {
 char str[100];
 int freq[256] = {0};
 int i, max = 0, ascii;

 printf("Enter a string: ");
 fgets(str, sizeof(str), stdin);
 str[strcspn(str, "\n")] = 0;

 for (i = 0; str[i] != '\0'; i++) {
 ascii = (int)str[i];
 freq[ascii]++;
 }

 for (i = 0; i < 256; i++) {
 if (freq[i] > freq[max]) {
 max = i;
 }
 }

 printf("Most frequent character: %c\n", (char)max);
 printf("Frequency: %d\n", freq[max]);

 return 0;
}

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Character Frequency in String

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

int main() {
 char str[100];
 int freq[256] = {0};
 int i;

 printf("Enter a string: ");
 fgets(str, sizeof(str), stdin);
 str[strcspn(str, "\n")] = 0;

 for (i = 0; str[i] != '\0'; i++) {
 freq[str[i]]++;
 }

 printf("Character frequencies:\n");
 for (i = 0; i < 256; i++) {
 if (freq[i] != 0) {
 printf("'%c': %d\n", i, freq[i]);
 }
 }

 return 0;
}

String Rotation Check

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

bool areRotations(char *str1, char *str2) {
  int n = strlen(str1);
  int m = strlen(str2);
  if (n != m) return false;
  char temp[2 * n + 1];
  strcpy(temp, str1);
  strcat(temp, str1);
  if (strstr(temp, str2) != NULL) return true;
  return false;
}

int main() {
  char str1[] = "ABCD";
  char str2[] = "CDAB";
  if (areRotations(str1, str2))
    printf("Strings are rotations of each other");
  else
    printf("Strings are not rotations of each other");
  return 0;
}

First Non-Repeating Character in a String

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

char findFirstNonRepeating(const char *str) {
 int counts[256] = {0};
 int len = strlen(str);
 for (int i = 0; i < len; i++) {
 counts[(unsigned char)str[i]]++;
 }
 for (int i = 0; i < len; i++) {
 if (counts[(unsigned char)str[i]] == 1) {
 return str[i];
 }
 }
 return '\0';
}

int main() {
 char str[] = "programming";
 char result = findFirstNonRepeating(str);
 if (result != '\0') {
 printf("First non-repeating char: %c\n", result);
 } else {
 printf("No non-repeating character found.\n");
 }
 return 0;
}

Anagram String Checker

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

bool areAnagrams(char str1[], char str2[]) {
    int n1 = strlen(str1);
    int n2 = strlen(str2);

    if (n1 != n2)
        return false;

    int count[256] = {0};
    for (int i = 0; str1[i] && str2[i]; i++) {
        count[str1[i]]++;
        count[str2[i]]--;
    }

    for (int i = 0; i < 256; i++)
        if (count[i])
            return false;

    return true;
}

int main() {
    char str1[100], str2[100];
    printf("Enter first string: ");
    scanf("%s", str1);
    printf("Enter second string: ");
    scanf("%s", str2);

    if (areAnagrams(str1, str2))
        printf("\"%s\" and \"%s\" are anagrams\n", str1, str2);
    else
        printf("\"%s\" and \"%s\" are not anagrams\n", str1, str2);

    return 0;
}

Find Duplicate Characters in a String

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

int main() {
 char str[100];
 int i, j, len;

 printf("Enter a string: ");
 fgets(str, sizeof(str), stdin);
 str[strcspn(str, "\n")] = 0;

 len = strlen(str);

 printf("Duplicate characters are: ");
 for (i = 0; i < len; i++) {
 for (j = i + 1; j < len; j++) {
 if (str[i] == str[j]) {
 printf("%c ", str[i]);
 break;
 }
 }
 }
 printf("\n");

 return 0;
}