C Programming Language || Hands On Coding

#include <stdio.h>

void swap(int *x, int *y) {
    *x = *x ^ *y;
    *y = *x ^ *y;
    *x = *x ^ *y;
}

int main() {
    int a = 10, b = 5;
    swap(&a, &b);
    printf("a = %d, b = %d\n", a, b);
    return 0;
}

#include <stdio.h>

long long factorial(int n) {
    if (n == 0)
        return 1;
    else
        return n * factorial(n - 1);
}

long long nCr(int n, int r) {
    if (r < 0 || r > n)
        return 0;
    if (r == 0 || r == n)
        return 1;
    if (r > n / 2)
        r = n - r;
    return factorial(n) / (factorial(r) * factorial(n - r));
}

int main() {
    int n, r;
    printf("Enter n and r: ");
    scanf("%d %d", &n, &r);
    printf("nCr = %lld\n", nCr(n, r));
    return 0;
}

#include <stdio.h>

int main() {
  int rows, coef = 1, space, i, j;

  scanf("%d", &rows);

  for (i = 0; i < rows; i++) {
    for (space = 1; space <= rows - i; space++)
      printf("  ");

    for (j = 0; j <= i; j++) {
      if (j == 0 || i == 0)
        coef = 1;
      else
        coef = coef * (i - j + 1) / j;

      printf("%4d", coef);
    }
    printf("\n");
  }

  return 0;
}

#include <stdio.h>

int sumOfFirstNEven(int n) {
    return n * (n + 1);
}

int sumOfFirstNOdd(int n) {
    return n * n;
}

int main() {
    int n;
    printf("Enter a number: ");
    scanf("%d", &n);
    printf("Sum of first %d even numbers: %d\n", n, sumOfFirstNEven(n));
    printf("Sum of first %d odd numbers: %d\n", n, sumOfFirstNOdd(n));
    return 0;
}

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

bool isPalindrome(int n) {
    int reversed = 0, original = n, remainder;
    while (n != 0) {
        remainder = n % 10;
        reversed = reversed * 10 + remainder;
        n /= 10;
    }
    return original == reversed;
}

bool isPrime(int n) {
    if (n <= 1) return false;
    for (int i = 2; i <= sqrt(n); i++) {
        if (n % i == 0) return false;
    }
    return true;
}

bool isPalindromicPrime(int n) {
    return isPalindrome(n) && isPrime(n);
}

int main() {
    int num;
    scanf("%d", &num);
    if (isPalindromicPrime(num)) {
        printf("True\n");
    } else {
        printf("False\n");
    }
    return 0;
}

#include <stdio.h>

int countTrailingZeroes(int n) {
  int count = 0;
  for (int i = 5; n / i >= 1; i *= 5) {
    count += n / i;
  }
  return count;
}

int main() {
  int num = 25;
  printf("Trailing zeroes in %d! = %d\n", num, countTrailingZeroes(num));
  return 0;
}

#include <stdio.h>
#include <math.h>

int binaryToDecimal(long long n) {
    int decimalNumber = 0, i = 0, remainder;
    while (n!=0) {
        remainder = n%10;
        n /= 10;
        decimalNumber += remainder*pow(2,i);
        ++i;
    }
    return decimalNumber;
}

int main() {
    long long n;
    printf("Enter a binary number: ");
    scanf("%lld", &n);
    printf("Decimal equivalent: %d", binaryToDecimal(n));
    return 0;
}

#include <stdio.h>

void decimalToBinary(int n) {
    int binary[32];
    int i = 0;
    while (n > 0) {
        binary[i] = n % 2;
        n = n / 2;
        i++;
    }
    for (int j = i - 1; j >= 0; j--)
        printf("%d", binary[j]);
    printf("\n");
}

void decimalToOctal(int n) {
    int octal[32];
    int i = 0;
    while (n > 0) {
        octal[i] = n % 8;
        n = n / 8;
        i++;
    }
    for (int j = i - 1; j >= 0; j--)
        printf("%d", octal[j]);
    printf("\n");
}

void decimalToHexadecimal(int n) {
    char hex[32];
    int i = 0;
    while (n != 0) {
        int temp = 0;
        temp = n % 16;
        if (temp < 10) {
            hex[i] = temp + 48;
        } else {
            hex[i] = temp + 87;
        }
        n = n / 16;
        i++;
    }
    for (int j = i - 1; j >= 0; j--)
        printf("%c", hex[j]);
    printf("\n");
}

int main() {
    int decimal;
    printf("Enter a decimal number: ");
    scanf("%d", &decimal);

    printf("Binary: ");
    decimalToBinary(decimal);

    printf("Octal: ");
    decimalToOctal(decimal);

    printf("Hexadecimal: ");
    decimalToHexadecimal(decimal);

    return 0;
}