C Programming Codes

#CProgramming #Algorithms #Exponentiation

Fast Exponentiation (Binary Exponentiation)

#include <stdio.h>

long long power(long long base, long long exp, long long mod) {
    long long res = 1;
    base %= mod;
    while (exp > 0) {
        if (exp % 2 == 1)
            res = (res * base) % mod;
        base = (base * base) % mod;
        exp /= 2;
    }
    return res;
}

int main() {
    long long base = 2;
    long long exp = 10;
    long long mod = 1000000007;
    long long result = power(base, exp, mod);
    printf("%lld\n", result);
    return 0;
}

#CProgramming #GCD #Arrays

GCD of Array Elements

#include <stdio.h>

int gcd(int a, int b) {
    if (b == 0) {
        return a;
    }
    return gcd(b, a % b);
}

int gcd_array(int arr[], int n) {
    int result = arr[0];
    for (int i = 1; i < n; i++) {
        result = gcd(result, arr[i]);
    }
    return result;
}

int main() {
    int arr[] = {12, 18, 24, 30};
    int n = sizeof(arr) / sizeof(arr[0]);
    int result = gcd_array(arr, n);
    printf("GCD of the array is: %d\n", result);
    return 0;
}

#CProgramming #LCM #GCD

LCM of Two Numbers

#include <stdio.h>

int gcd(int a, int b) {
    if (b == 0)
        return a;
    return gcd(b, a % b);
}

int lcm(int a, int b) {
    return (a * b) / gcd(a, b);
}

int main() {
    int num1, num2;
    scanf("%d %d", &num1, &num2);
    printf("%d\n", lcm(num1, num2));
    return 0;
}

#CProgramming #GCD #EuclideanAlgorithm

GCD of Two Numbers (Euclidean Algorithm)

#include <stdio.h>

int gcd(int a, int b) {
  while (b != 0) {
    int temp = b;
    b = a % b;
    a = temp;
  }
  return a;
}

int main() {
  int num1, num2;
  printf("Enter two integers: ");
  scanf("%d %d", &num1, &num2);
  printf("GCD of %d and %d is %d\n", num1, num2, gcd(num1, num2));
  return 0;
}

#CProgramming #StrongNumber #InterviewPrep

Check Strong Number

#include <stdio.h>

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

int isStrong(int num) {
    int sum = 0, temp = num, digit;
    while (temp > 0) {
        digit = temp % 10;
        sum += factorial(digit);
        temp /= 10;
    }
    return (sum == num);
}

int main() {
    int number;
    scanf("%d", &number);
    if (isStrong(number))
        printf("Strong Number\n");
    else
        printf("Not Strong Number\n");
    return 0;
}

#CProgramming #DigitsCount #InterviewPrep

Count Digits Without % or /

#include <stdio.h>

int countDigits(int n) {
  int count = 0;
  if (n == 0) return 1;
  while (n > 0) {
    n = n - (n / 10) * 10;
    n = n / 10;
    count++;
  }
  return count;
}

int main() {
  int num = 12345;
  int digitCount = countDigits(num);
  printf("Number of digits in %d is %d\n", num, digitCount);
  return 0;
}

#CProgramming #PrimeNumbers

Check Prime Number in Range

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

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

void printPrimesInRange(int start, int end) {
 for (int i = start; i <= end; i++) {
 if (isPrime(i)) {
 printf("%d ", i);
 }
 }
 printf("\n");
}

int main() {
 int start, end;
 printf("Enter the start of the range: ");
 scanf("%d", &start);
 printf("Enter the end of the range: ");
 scanf("%d", &end);
 printf("Prime numbers in the range %d to %d are: ", start, end);
 printPrimesInRange(start, end);
 return 0;
}

#CProgramming #DigitsCount #InterviewPrep

Count Digits Without % or /

#include <stdio.h>

int countDigits(int n) {
  int count = 0;
  if (n == 0) return 1;
  while (n > 0) {
    n = n - (n / 10) * 10;
    n = n / 10;
    count++;
  }
  return count;
}

int main() {
  int num = 12345;
  int digitCount = countDigits(num);
  printf("Number of digits in %d is %d\n", num, digitCount);
  return 0;
}

#CProgramming #PerfectNumber #Algorithm

Check Perfect Number

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

bool isPerfect(int num) {
 if (num <= 1) return false;
 int sum = 1;
 for (int i = 2; i * i <= num; i++) {
 if (num % i == 0) {
 sum += i;
 if (i * i != num) {
 sum += num / i;
 }
 }
 }
 return sum == num;
}

int main() {
 int number;
 scanf("%d", &number);
 if (isPerfect(number)) {
 printf("%d is a perfect number.\n", number);
 } else {
 printf("%d is not a perfect number.\n", number);
 }
 return 0;
}

#CProgramming #ArmstrongNumber #InterviewPrep

Check Armstrong Number (n digits)

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

int main() {
    int num, originalNum, remainder, n = 0;
    float result = 0.0;

    printf("Enter an integer: ");
    scanf("%d", &num);

    originalNum = num;

    while (originalNum != 0) {
        originalNum /= 10;
        ++n;
    }

    originalNum = num;

    while (originalNum != 0) {
        remainder = originalNum % 10;
        result += pow(remainder, n);
        originalNum /= 10;
    }

    if ((int)result == num)
        printf("%d is an Armstrong number.\n", num);
    else
        printf("%d is not an Armstrong number.\n", num);

    return 0;
}