C Programming Codes

#CProgramming #MathTrick #Algorithm

Efficiently calculate the sum of numbers from 1 to N in C?

#include <stdio.h>int main() {    int n = 10;    int sum = (n * (n + 1)) / 2;    printf("Sum of numbers from 1 to %d is: %d\n", n, sum);    return 0;}

#CProgramming #Bitwise #PowerOfTwo

How to check if a number is a power of 2 efficiently?

#include <stdio.h>#include <stdbool.h>bool isPowerOfTwo(int n) {    return (n > 0) && ((n & (n - 1)) == 0);}int main() {    int num = 16;    if (isPowerOfTwo(num)) {        printf("%d is a power of 2\n", num);    } else {        printf("%d is not a power of 2\n", num);    }    return 0;}

#CProgramming #Pointers #CallByReference

Pointers in C: Can you modify a variable outside a function?

#include <stdio.h>

void increment(int *n) {
  (*n)++;
}

int main() {
  int num = 10;
  printf("Before: %d\n", num);
  increment(&num);
  printf("After: %d\n", num);
  return 0;
}

#CProgramming #DynamicArrays #Malloc

Function to Return Dynamic Array (malloc)

#include <stdio.h>
#include <stdlib.h>

int* create_dynamic_array(int size) {
    if (size <= 0) {
        return NULL; 
    }
    int* arr = (int*)malloc(size * sizeof(int));
    if (arr == NULL) {
        return NULL; 
    }
    for (int i = 0; i < size; i++) {
        arr[i] = i + 1; 
    }
    return arr;
}

int main() {
    int size = 5;
    int* my_array = create_dynamic_array(size);
    if (my_array != NULL) {
        for (int i = 0; i < size; i++) {
            printf("%d ", my_array[i]);
        }
        printf("\n");
        free(my_array);
        my_array = NULL; 
    }
    return 0;
}

#CProgramming #Pointers #DynamicMemory

Pointer to Pointer (Double Pointer)

#include <stdio.h>
#include <stdlib.h>

int main() {
    int x = 10;
    int *ptr = &x;
    int **ptr_to_ptr = &ptr;

    printf("Value of x: %d\n", x);
    printf("Address of x: %p\n", &x);
    printf("Value of ptr: %p\n", ptr);
    printf("Value pointed to by ptr: %d\n", *ptr);
    printf("Address of ptr: %p\n", &ptr);
    printf("Value of ptr_to_ptr: %p\n", ptr_to_ptr);
    printf("Value pointed to by ptr_to_ptr: %p\n", *ptr_to_ptr);
    printf("Value pointed to by *ptr_to_ptr: %d\n", **ptr_to_ptr);
    printf("Address of ptr_to_ptr: %p\n", &ptr_to_ptr);

    // Example: Dynamically allocate an array of strings
    int num_strings = 3;
    char **string_array = (char **)malloc(num_strings * sizeof(char *));

    if (string_array == NULL) {
        perror("malloc failed");
        return 1;
    }

    string_array[0] = (char *)malloc(10 * sizeof(char));
    string_array[1] = (char *)malloc(15 * sizeof(char));
    string_array[2] = (char *)malloc(20 * sizeof(char));

    if (string_array[0] == NULL || string_array[1] == NULL || string_array[2] == NULL) {
        perror("malloc failed");
        // Free previously allocated memory to avoid memory leaks
        for(int i = 0; i < num_strings; ++i){
            if(string_array[i] != NULL){
                free(string_array[i]);
            }
        }
        free(string_array);
        return 1;
    }

    sprintf(string_array[0], "Hello");
    sprintf(string_array[1], "World!");
    sprintf(string_array[2], "Double Pointers");

    for (int i = 0; i < num_strings; i++) {
        printf("string_array[%d] = %s\n", i, string_array[i]);
    }

    // Free dynamically allocated memory
    for (int i = 0; i < num_strings; i++) {
        free(string_array[i]);
    }
    free(string_array);

    return 0;
}

#CProgramming #Arrays #Pointers

Array Traversal with Pointers

#include <stdio.h>

int main() {
    int arr[] = {10, 20, 30, 40, 50};
    int *ptr = arr;
    int size = sizeof(arr) / sizeof(arr[0]);

    printf("Array elements:\n");
    for (int i = 0; i < size; i++) {
        printf("Element %d: %d\n", i, *ptr);
        ptr++;
    }

    ptr = arr; 
    printf("Array elements (using pointer arithmetic):\n");
    for (int i = 0; i < size; i++) {
        printf("Element %d: %d\n", i, *(arr + i));
    }

    return 0;
}

#CProgramming #Pointers #SwapVariables

Swap Variables Using Pointers

#include <stdio.h>

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

int main() {
    int a = 10;
    int b = 20;

    printf("Before swap: a = %d, b = %d\n", a, b);
    swap(&a, &b);
    printf("After swap: a = %d, b = %d\n", a, b);

    return 0;
}

#CProgramming #StringLength #Pointers

String Length using Pointer Arithmetic

#include <stdio.h>

int stringLength(const char *str) {
    const char *p = str;
    while (*p != '\0') {
        p++;
    }
    return p - str;
}

int main() {
    char str[] = "Hello, World!";
    int len = stringLength(str);
    printf("Length of the string: %d\n", len);
    return 0;
}

#CProgramming #Pointers #ArrayReverse

Reverse Array using Pointers

#include <stdio.h>

void reverseArray(int *arr, int size) {
    int *start = arr;
    int *end = arr + size - 1;
    int temp;

    while (start < end) {
        temp = *start;
        *start = *end;
        *end = temp;
        start++;
        end--;
    }
}

int main() {
    int arr[] = {1, 2, 3, 4, 5};
    int size = sizeof(arr) / sizeof(arr[0]);

    reverseArray(arr, size);

    printf("Reversed array: ");
    for (int i = 0; i < size; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");

    return 0;
}

#CProgramming #BitwiseOperators #AdditionWithoutPlus

Add Two Numbers Without + Operator

#include <stdio.h>

int add(int x, int y) {
    while (y != 0) {
        int carry = x & y;
        x = x ^ y;
        y = carry << 1;
    }
    return x;
}

int main() {
    int num1 = 5;
    int num2 = 10;
    int sum = add(num1, num2);
    printf("Sum of %d and %d is %d\n", num1, num2, sum);
    return 0;
}