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| 1 | +/** |
| 2 | + * @brief Program to generate n-bit [Gray |
| 3 | + * code](https://en.wikipedia.org/wiki/Gray_code) |
| 4 | + * |
| 5 | + * @details |
| 6 | + * Gray code is a binary numeral system |
| 7 | + * where consecutive values differ in exactly 1 bit. |
| 8 | + * The following code offers one of many possible Gray codes |
| 9 | + * given some pre-determined number of bits. |
| 10 | + */ |
| 11 | + |
| 12 | +#include <bitset> /// for gray code representation |
| 13 | +#include <cassert> /// for assert |
| 14 | +#include <iostream> /// for IO operations |
| 15 | +#include <vector> /// for vector data structure |
| 16 | + |
| 17 | +/** |
| 18 | + * @namespace bit_manipulation |
| 19 | + * @brief Bit manipulation algorithms |
| 20 | + */ |
| 21 | +namespace bit_manipulation { |
| 22 | +/** |
| 23 | + * @namespace gray_code |
| 24 | + * @brief Generate n-bit Gray code |
| 25 | + */ |
| 26 | +namespace gray_code { |
| 27 | +/** |
| 28 | + * @brief The main function to generate n-bit Gray code |
| 29 | + * |
| 30 | + * @param n Number of bits |
| 31 | + * @return A vector that stores the n-bit Gray code |
| 32 | + */ |
| 33 | +std::vector<std::bitset<32>> gray_code_generation(int n) { |
| 34 | + std::vector<std::bitset<32>> gray_code = {}; // Initialise empty vector |
| 35 | + |
| 36 | + // No Gray codes for non-positive values of n |
| 37 | + if (n <= 0) { |
| 38 | + return gray_code; |
| 39 | + } |
| 40 | + |
| 41 | + int total_codes = 1 << n; // Number of n-bit gray codes |
| 42 | + |
| 43 | + for (int i = 0; i < total_codes; i++) { |
| 44 | + int gray_num = i ^ (i >> 1); // Gray code formula |
| 45 | + gray_code.push_back(std::bitset<32>(gray_num)); // Store the value |
| 46 | + } |
| 47 | + |
| 48 | + return gray_code; |
| 49 | +} |
| 50 | +} // namespace gray_code |
| 51 | +} // namespace bit_manipulation |
| 52 | + |
| 53 | +/** |
| 54 | + * @brief Self-test implementation |
| 55 | + * |
| 56 | + * @returns void |
| 57 | + */ |
| 58 | +static void test() { |
| 59 | + std::vector<std::bitset<32>> gray_code_negative_1 = {}; |
| 60 | + |
| 61 | + std::vector<std::bitset<32>> gray_code_0 = {}; |
| 62 | + |
| 63 | + std::vector<std::bitset<32>> gray_code_1 = { |
| 64 | + std::bitset<32>(0), std::bitset<32>(1) |
| 65 | + }; |
| 66 | + |
| 67 | + std::vector<std::bitset<32>> gray_code_2 = { |
| 68 | + std::bitset<32>(0), std::bitset<32>(1), std::bitset<32>(3), std::bitset<32>(2) |
| 69 | + }; |
| 70 | + |
| 71 | + std::vector<std::bitset<32>> gray_code_3 = { |
| 72 | + std::bitset<32>(0), std::bitset<32>(1), std::bitset<32>(3), std::bitset<32>(2), |
| 73 | + std::bitset<32>(6), std::bitset<32>(7), std::bitset<32>(5), std::bitset<32>(4) |
| 74 | + }; |
| 75 | + |
| 76 | + std::vector<std::bitset<32>> gray_code_4 = { |
| 77 | + std::bitset<32>(0), std::bitset<32>(1), std::bitset<32>(3), std::bitset<32>(2), |
| 78 | + std::bitset<32>(6), std::bitset<32>(7), std::bitset<32>(5), std::bitset<32>(4), |
| 79 | + std::bitset<32>(12), std::bitset<32>(13), std::bitset<32>(15), std::bitset<32>(14), |
| 80 | + std::bitset<32>(10), std::bitset<32>(11), std::bitset<32>(9), std::bitset<32>(8) |
| 81 | + }; |
| 82 | + |
| 83 | + std::vector<std::bitset<32>> gray_code_5 = { |
| 84 | + std::bitset<32>(0), std::bitset<32>(1), std::bitset<32>(3), std::bitset<32>(2), |
| 85 | + std::bitset<32>(6), std::bitset<32>(7), std::bitset<32>(5), std::bitset<32>(4), |
| 86 | + std::bitset<32>(12), std::bitset<32>(13), std::bitset<32>(15), std::bitset<32>(14), |
| 87 | + std::bitset<32>(10), std::bitset<32>(11), std::bitset<32>(9), std::bitset<32>(8), |
| 88 | + std::bitset<32>(24), std::bitset<32>(25), std::bitset<32>(27), std::bitset<32>(26), |
| 89 | + std::bitset<32>(30), std::bitset<32>(31), std::bitset<32>(29), std::bitset<32>(28), |
| 90 | + std::bitset<32>(20), std::bitset<32>(21), std::bitset<32>(23), std::bitset<32>(22), |
| 91 | + std::bitset<32>(18), std::bitset<32>(19), std::bitset<32>(17), std::bitset<32>(16) |
| 92 | + }; |
| 93 | + |
| 94 | + // invalid values for n |
| 95 | + assert(bit_manipulation::gray_code::gray_code_generation(-1) == gray_code_negative_1); |
| 96 | + assert(bit_manipulation::gray_code::gray_code_generation(0) == gray_code_0); |
| 97 | + |
| 98 | + // valid values for n |
| 99 | + assert(bit_manipulation::gray_code::gray_code_generation(1) == gray_code_1); |
| 100 | + assert(bit_manipulation::gray_code::gray_code_generation(2) == gray_code_2); |
| 101 | + assert(bit_manipulation::gray_code::gray_code_generation(3) == gray_code_3); |
| 102 | + assert(bit_manipulation::gray_code::gray_code_generation(4) == gray_code_4); |
| 103 | + assert(bit_manipulation::gray_code::gray_code_generation(5) == gray_code_5); |
| 104 | +} |
| 105 | + |
| 106 | +/** |
| 107 | + * @brief Main function |
| 108 | + * @returns 0 on exit |
| 109 | + */ |
| 110 | +int main() { |
| 111 | + test(); //Run self-test implementation |
| 112 | + return 0; |
| 113 | +} |
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