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| 1 | +/** |
| 2 | + * @file |
| 3 | + * @brief Implementation to [Check if a number is Even or Odd using Bitwise Operator] |
| 4 | + * (https://www.log2base2.com/c-examples/bitwise/odd-or-even-program-in-c-using-bitwise-operator.html) |
| 5 | + * |
| 6 | + * @details |
| 7 | + * Given an integer N, determine whether it is even or odd using bitwise manipulation. |
| 8 | + * The least significant bit (LSB) of a binary number determines its parity: |
| 9 | + * - If the LSB is 0, the number is even. |
| 10 | + * - If the LSB is 1, the number is odd. |
| 11 | + * |
| 12 | + * This can be checked efficiently using the bitwise AND operator (&) with 1. |
| 13 | + * - If (N & 1) == 0, N is even. |
| 14 | + * - If (N & 1) == 1, N is odd. |
| 15 | + * |
| 16 | + * Example: |
| 17 | + * Consider 8-bit binary representations of two numbers: |
| 18 | + * Number: 10 (decimal) -> 00001010 (binary) |
| 19 | + * LSB = 0 -> Even number |
| 20 | + * |
| 21 | + * Number: 13 (decimal) -> 00001101 (binary) |
| 22 | + * LSB = 1 -> Odd number |
| 23 | + * |
| 24 | + * In both cases, evaluating (N & 1) isolates the LSB: |
| 25 | + * - For 10: 00001010 & 00000001 = 0 (Even) |
| 26 | + * - For 13: 00001101 & 00000001 = 1 (Odd) |
| 27 | + * |
| 28 | + * Worst Case Time Complexity: O(1) |
| 29 | + * Space Complexity: O(1) |
| 30 | + * |
| 31 | + * @author [Vedant Mukhedkar](https://github.com/git5v) |
| 32 | + */ |
| 33 | + |
| 34 | +#include <cassert> /// for assert |
| 35 | +#include <cstdint> /// for uint32_t |
| 36 | +#include <iostream> /// for IO operations |
| 37 | +#include <string> /// for std::string |
| 38 | + |
| 39 | +/** |
| 40 | + * @namespace bit_manipulation |
| 41 | + * @brief Bit manipulation algorithms |
| 42 | + */ |
| 43 | +namespace bit_manipulation { |
| 44 | +/** |
| 45 | + * @namespace even_odd |
| 46 | + * @brief Functions for checking if a number is even or odd using bitwise operations |
| 47 | + */ |
| 48 | +namespace even_odd { |
| 49 | + |
| 50 | +/** |
| 51 | + * @brief Checks if a number is even or odd using bitwise AND. |
| 52 | + * @param N The number to check. |
| 53 | + * @returns "Even" if N is even, "Odd" if N is odd. |
| 54 | + */ |
| 55 | + bool is_even(std::int64_t N) { |
| 56 | + return (N & 1) == 0 ? true : false; |
| 57 | + } |
| 58 | + |
| 59 | + } // namespace even_odd |
| 60 | +} // namespace bit_manipulation |
| 61 | + |
| 62 | +/** |
| 63 | + * @brief Self-test implementations |
| 64 | + * @returns void |
| 65 | + */ |
| 66 | +static void test() { |
| 67 | + using bit_manipulation::even_odd::is_even; |
| 68 | + |
| 69 | + // Test Even numbers |
| 70 | + assert(is_even(0) == true); |
| 71 | + assert(is_even(2) == true); |
| 72 | + assert(is_even(100) == true); |
| 73 | + assert(is_even(-4) == true); |
| 74 | + assert(is_even(-1000) == true); |
| 75 | + |
| 76 | + // Test Odd numbers |
| 77 | + assert(is_even(1) == false); |
| 78 | + assert(is_even(3) == false); |
| 79 | + assert(is_even(101) == false); |
| 80 | + assert(is_even(-5) == false); |
| 81 | + assert(is_even(-999) == false); |
| 82 | + |
| 83 | + std::cout << "All test cases successfully passed!" << std::endl; |
| 84 | +} |
| 85 | + |
| 86 | +/** |
| 87 | + * @brief Main function |
| 88 | + * @returns 0 on exit |
| 89 | + */ |
| 90 | +int main() { |
| 91 | + test(); // run self-test implementations |
| 92 | + return 0; |
| 93 | +} |
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