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[Kata 7 C++]Binary Addition

发布时间:2023/6/3 16:46:47

描述

Implement a function that adds two numbers together and returns their sum in binary. The conversion can be done before, or after the addition.

The binary number returned should be a string.

Examples:(Input1, Input2 --> Output (explanation)))

1, 1 --> "10" (1 + 1 = 2 in decimal or 10 in binary)
5, 9 --> "1110" (5 + 9 = 14 in decimal or 1110 in binary)

测试用例

#include <random>
#include <string>
#include <tuple>
#include <cstdint>
#include <sstream>Describe(FixedTests)
{It(should_pass_fixed_tests){Assert::That(add_binary(1, 1), Equals("10"), ExtraMessage("Invalid result for a = 1, b = 1"));Assert::That(add_binary(0, 1), Equals("1"), ExtraMessage("Invalid result for a = 0, b = 1"));Assert::That(add_binary(1, 0), Equals("1"), ExtraMessage("Invalid result for a = 1, b = 0"));Assert::That(add_binary(2, 2), Equals("100"), ExtraMessage("Invalid result for a = 2, b = 2"));Assert::That(add_binary(51, 12), Equals("111111"), ExtraMessage("Invalid result for a = 51, b = 12"));Assert::That(add_binary(5, 9), Equals("1110"), ExtraMessage("Invalid result for a = 5, b = 9"));Assert::That(add_binary(10, 10), Equals("10100"), ExtraMessage("Invalid result for a = 10, b = 10"));Assert::That(add_binary(100, 100), Equals("11001000"), ExtraMessage("Invalid result for a = 100, b = 100"));Assert::That(add_binary(4096, 1), Equals("1000000000001"), ExtraMessage("Invalid result for a = 4096, b = 1"));Assert::That(add_binary(0, 2174483647), Equals("10000001100110111111110010111111"), ExtraMessage("Invalid result for a = 0, b = 2174483647"));}It(should_handle_edge_case){Assert::That(add_binary(0, 0), Equals("0"), ExtraMessage("Invalid result for a = 0, b = 0"));}
};Describe(RandomTests)
{
private:std::mt19937 engine{ std::random_device{}() };std::uniform_int_distribution<size_t> dist_l{ 0, 64 };std::uniform_int_distribution<char> dist_b{ 0, 1 };std::tuple<uint64_t, uint64_t, std::string> generate_problem(){        const size_t len = dist_l(engine);if(len == 0) return { 0, 0, "0" };std::string res = "1";uint64_t sum = 1;for(size_t i = 1; i < len; ++i){const bool d = dist_b(engine);res += static_cast<char>(d + '0');sum = sum << 1 | d;}const auto a = std::uniform_int_distribution<uint64_t>{ 0, sum }(engine);return { a, sum - a, res };}public:It(should_pass_random_tests){for(int i = 0; i < 100; ++i){const auto [a, b, res] = generate_problem();const auto msg = [a = a, b = b]{std::ostringstream res;res << "Incorrect result for a = " << a << ", b = " << b;return res.str();};Assert::That(add_binary(a, b), Equals(res), msg);}}
};

解决方案:

format

#include <cstdint>
#include <string>
#include <fmt/core.h>std::string add_binary(std::uint64_t a, std::uint64_t b) {return fmt::format("{:b}", a + b);
}

fmt 是一个三方库

字符串拼接

#include <cstdint>
#include <string>using namespace std;string add_binary(uint64_t a, uint64_t b) {a += b;string output;do {output = to_string(a % 2) + output;a /= 2;} while(a > 0);return output;
}

连续拼接字符串会产生大量对象,如果利用append 最后 reverce 会快一点。

bitset

#include <cstdint>
#include <string>
#include <bitset>using namespace std;std::string add_binary(uint64_t a, uint64_t b) {string bi = std::bitset<64>((a + b)).to_string();return bi.erase(0, min(bi.find_first_not_of('0'), bi.size()-1));
}

bitset库
C++的 bitset 在 bitset 头文件中,它是一种类似数组的结构,它的每一个元素只能是0或1,每个元素仅用1bit空间。
用字符串构造时,字符串只能包含 ‘0’ 或 ‘1’ ,否则会抛出异常。
构造时,需在<>中表明bitset 的大小(即size)。
在进行有参构造时,若参数的二进制表示比bitset的size小,则在前面用0补充;若比bitsize大,参数为整数时取后面部分,参数为字符串时取前面部分
构造函数:

  bitset<4> bitset1;  //无参构造,长度为4,默认每一位为0bitset<8> bitset2(12);  //长度为8,二进制保存,前面用0补充string s = "100101";bitset<10> bitset3(s);  //长度为10,前面用0补充char s2[] = "10101";bitset<13> bitset4(s2);  //长度为13,前面用0补充

方法:

 bitset<8> foo ("10011011");cout << foo.count() << endl;  //5  (count函数用来求bitset中1的位数,foo中共有5个1cout << foo.size() << endl;   //8  (size函数用来求bitset的大小,一共有8位cout << foo.test(0) << endl;  //true  (test函数用来查下标处的元素是0还是1,并返回false或true,此处foo[0]为1,返回truecout << foo.test(2) << endl;  //false  (同理,foo[2]为0,返回falsecout << foo.any() << endl;  //true  (any函数检查bitset中是否有1cout << foo.none() << endl;  //false  (none函数检查bitset中是否没有1cout << foo.all() << endl;  //false  (all函数检查bitset中是全部为1cout << foo.flip(2) << endl;  //10011111  (flip函数传参数时,用于将参数位取反,本行代码将foo下标2处"反转",即0变1,1变0cout << foo.flip() << endl;   //01100000  (flip函数不指定参数时,将bitset每一位全部取反cout << foo.set() << endl;    //11111111  (set函数不指定参数时,将bitset的每一位全部置为1cout << foo.set(3,0) << endl;  //11110111  (set函数指定两位参数时,将第一参数位的元素置为第二参数的值,本行对foo的操作相当于foo[3]=0cout << foo.set(3) << endl;    //11111111  (set函数只有一个参数时,将参数下标处置为1cout << foo.reset(4) << endl;  //11101111  (reset函数传一个参数时将参数下标处置为0cout << foo.reset() << endl;   //00000000  (reset函数不传参数时将bitset的每一位全部置为0string s = foo.to_string();  //将bitset转换成string类型unsigned long a = foo.to_ulong();  //将bitset转换成unsigned long类型unsigned long long b = foo.to_ullong();  //将bitset转换成unsigned long long类型

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