题解 | #10进制 VS 2进制#

//土尔逊Torson 编写于2023/5/04
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cstdio>
#include <string>
#include <vector>

using namespace std;

string Divide06001(string str, int x) { //字符串除法
	int remainder = 0;             //保存余数
	for (int i = 0; i < str.size(); ++i) {
		int current = remainder * 10 + str[i] - '0';
		str[i] = current / x + '0';
		remainder = current % x;
	}
	int pos = 0;
	while (str[pos] == '0') {       //寻找首个非0下标
		pos++;
	}
	return str.substr(pos);         //删除前置多余的0
}

string Multiple(string str, int x) {             //字符串乘法
	int carry = 0;                               //保存进位
	for (int i = str.size() - 1; i >= 0; --i) {
		int current = x*(str[i] - '0') + carry;
		str[i] = current % 10 + '0';
		carry = current / 10;
	}
	if (carry != 0) {                            //仍有进位
		str = "1" + str;
	}
	return str;
}

string Add(string str, int x) {                  //字符串加法
	int carry = x;
	for (int i = str.size() - 1; i >= 0; --i) {
		int current = (str[i] - '0') + carry;
		str[i] = current % 10 + '0';
		carry = current / 10;
	}
	if (carry != 0) {                            //仍有进位
		str = "1" + str;
	}
	return str;
}

int main() {
	string str;
	while (cin >> str) {
		vector<int> binary;
		while (str.size() != 0) {
			int last = str[str.size() - 1] - '0'; //最低位的值
			binary.push_back(last % 2);           //取模运算
			str = Divide06001(str, 2);                 //整除运算
		}
		string answer = "0";
		for (int i = 0; i < binary.size(); ++i) {
			answer = Multiple(answer, 2);         //乘法运算
			answer = Add(answer, binary[i]);      //加法运算
		}
		cout << answer << endl;
	}
	system("pause");
	return EXIT_SUCCESS;
}
// 64 位输出请用 printf("%lld")