C Programming Codes

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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;
}

Palindrome String Check (No strrev)

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

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

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

 len = strlen(str);

 for (i = 0; i < len/2; i++) {
 if (str[i] != str[len-i-1]) {
 flag = 0;
 break;
 }
 }

 if (flag) {
 printf("%s is a palindrome", str);
 } else {
 printf("%s is not a palindrome", str);
 }
 return 0;
}

Reverse a String

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

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

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

 len = strlen(str);

 for (i = 0; i < len/2; i++) {
 temp = str[i];
 str[i] = str[len - i - 1];
 str[len - i - 1] = temp;
 }

 printf("Reversed string: %s\n", str);
 return 0;
}

Remove Vowels from a String

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

bool isVowel(char c) {
    c = tolower(c);
    return (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u');
}

int main() {
    char str[100];
    printf("Enter a string: ");
    fgets(str, sizeof(str), stdin);
    str[strcspn(str, "\n")] = 0;

    int j = 0;
    for (int i = 0; str[i] != '\0'; i++) {
        if (!isVowel(str[i])) {
            str[j++] = str[i];
        }
    }
    str[j] = '\0';

    printf("String after removing vowels: %s\n", str);
    return 0;
}

Remove Spaces from String

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

void removeSpaces(char *str) {
    int i, j = 0;
    for (i = 0; str[i] != '\0'; i++) {
        if (str[i] != ' ') {
            str[j++] = str[i];
        }
    }
    str[j] = '\0';
}

int main() {
    char str[] = " This is a string with spaces. ";
    removeSpaces(str);
    printf("%s", str);
    return 0;
}

Toggle Case of String Characters

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

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

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

 for (i = 0; str[i] != '\0'; i++) {
 if (islower(str[i])) {
 str[i] = toupper(str[i]);
 } else if (isupper(str[i])) {
 str[i] = tolower(str[i]);
 }
 }

 printf("Toggled string: %s\n", str);
 return 0;
}

Count Vowels, Consonants, Digits, and Spaces in a String

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

int main() {
  char str[100];
  int vowels = 0, consonants = 0, digits = 0, spaces = 0;
  printf("Enter a string: ");
  fgets(str, sizeof(str), stdin);

  for (int i = 0; str[i] != '\0'; i++) {
    char ch = str[i];
    if ((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z')) {
      ch = (ch >= 'A' && ch <= 'Z') ? (ch + 32) : ch;
      if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
        vowels++;
      } else {
        consonants++;
      }
    } else if (ch >= '0' && ch <= '9') {
      digits++;
    } else if (ch == ' ') {
      spaces++;
    }
  }

  printf("Vowels: %d\n", vowels);
  printf("Consonants: %d\n", consonants);
  printf("Digits: %d\n", digits);
  printf("Spaces: %d\n", spaces);
  return 0;
}