AI Coding & CSE Fundamentals

#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;
}

#CProgramming #Bitwise #OddEven

Odd or Even using Bitwise Operator

#include <stdio.h>

int main() {
    int num = 7;
    if (num & 1) {
        printf("%d is odd.\n", num);
    } else {
        printf("%d is even.\n", num);
    }
    return 0;
}

#CProgramming #SetBits #LookupTable

Count Set Bits using Lookup Table

#include <stdio.h>
#include <stdint.h>

unsigned char setBits[256] = {
    0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
    1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
    1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
    1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
    3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
    1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
    3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
    2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
    3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
    3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
    4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8
};

int countSetBits(int n) {
    int count = 0;
    count += setBits[n & 0xFF];
    n >>= 8;
    count += setBits[n & 0xFF];
    n >>= 8;
    count += setBits[n & 0xFF];
    n >>= 8;
    count += setBits[n & 0xFF];
    return count;
}

int main() {
    int num = 0b10110011101011001101010111100010;
    printf("Number of set bits in %d is %d\n", num, countSetBits(num));
    return 0;
}

#CProgramming #BitManipulation #RightmostBit

Isolate Rightmost Set Bit

#include <stdio.h>

int isolateRightmostSetBit(int n) {
    return n & -n;
}

int main() {
    int num = 20; // Example number (binary 10100)
    int isolatedBit = isolateRightmostSetBit(num);
    printf("Original number: %d\n", num);
    printf("Rightmost set bit: %d\n", isolatedBit);
    return 0;
}

#CProgramming #BitwiseOperations #InterviewQuestion

Turn Off Rightmost Set Bit

#include <stdio.h>

int turnOffRightmostSetBit(int n) {
    return n & (n - 1);
}

int main() {
    int num = 12; 
    int result = turnOffRightmostSetBit(num);
    printf("Original number: %d\n", num);
    printf("Number with rightmost set bit turned off: %d\n", result);
    return 0;
}

#CProgramming #BitManipulation #RightmostBit

Find Position of Rightmost Set Bit

#include <stdio.h>

int findRightmostSetBit(unsigned int n) {
    if (n == 0) {
        return 0; 
    }
    int pos = 1;
    while ((n & 1) == 0) {
        n = n >> 1;
        pos++;
    }
    return pos;
}

int main() {
    unsigned int num = 12;  // Example number (1100 in binary)
    int position = findRightmostSetBit(num);
    printf("Rightmost set bit is at position: %d\n", position);
    return 0;
}

#CProgramming #BitManipulation #RightmostBit

Find Position of Rightmost Set Bit

#include <stdio.h>

int findRightmostSetBit(unsigned int n) {
    if (n == 0)
        return 0;
    int pos = 1;
    while ((n & 1) == 0) {
        n = n >> 1;
        pos++;
    }
    return pos;
}

int main() {
    unsigned int num = 12; // Example: 1100 in binary
    int position = findRightmostSetBit(num);
    printf("Rightmost set bit is at position: %d\n", position);
    return 0;
}

#CProgramming #BitManipulation

Check if Number has Only One Bit Set

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

bool isOnlyOneBitSet(int n) {
    if (n <= 0) {
        return false;
    }
    return (n & (n - 1)) == 0;
}

int main() {
    int num = 8;
    if (isOnlyOneBitSet(num)) {
        printf("%d has only one bit set.\n", num);
    } else {
        printf("%d does not have only one bit set.\n", num);
    }
    return 0;
}