题解 | #10进制 VS 2进制#

#include<iostream>
#include<string>
#include<vector>
using namespace std;

//例题6.3 KY26 10进制 VS 2进制 

//字符串表示的大整数除法
string divide(string str, int x) {
    int reminder = 0;
    for (int i = 0; i < str.size(); i++) {
        int current = reminder * 10 + str[i] - '0';
        str[i] = current / x + '0';
        reminder = current % x;
    }
    int pos = 0;
    while (str[pos] == '0') {
        pos++;
    }
    return str.substr(pos);
}

string multiple(string str, int x) {
    int carry = 0;
    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) {
        str = "1" + str;
    }
    return str;
}

string Add(string str, int x) {
    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) {
        str = "1" + str;
    }
    return str;
}

int main()
{
    string s;
    cin >> s;
    vector<int> binary;
    while (s.size() != 0) {
        int last = s[s.size() - 1]-'0';
        binary.push_back(last % 2);
        s = divide(s, 2);
    }

    string res = "0";
    for (int i = 0; i < binary.size(); i++) {
        res = multiple(res, 2);
        res = Add(res, binary[i]);
    }
    cout << res << endl;

   
    return 0;
}

// 64 位输出请用 printf("%lld")