2020年辽宁省省赛H 鸽子的浮点运算

鸽子的浮点运算

模拟

就跟着题意模拟就好了

先读入，然后转成二进制，截断成 \(16\) 位，然后转成十进制 \(double\)，最后计算，计算结果转成二进制截断成 \(16\) 位，然后输出

#include <iostream>
#include <cstdio>
#include <vector>
#include <string>
using namespace std;
typedef long long ll;
const ll mod = 1e9 + 7;

string fl_to_string(double x)
{
    ll pre = (ll)x;
    string now = "";
    while(pre)
    {
        if(pre & 1) now = "1" + now;
        else now = "0" + now;
        pre >>= 1;
    }
    int f = now.size();
    x -= (ll)x;
    for(int i=0; i<50; i++)
    {
        x *= 2.0;
        if(x >= 1) {now += "1"; x -= 1.0;}
        else now += "0";
    }
    string ans = "0";
    if(f)
    {
        ll cnt = f + 14;
        string temp = "";
        while(cnt)
        {
            if(cnt & 1) temp = "1" + temp;
            else temp = "0" + temp;
            cnt >>= 1;
        }
        while(temp.size() < 5) temp = "0" + temp;
        ans += temp;
        ans += string(now, 1, 10);
    }
    else
    {
        ll way = 0;
        while(now[way] == '0') way++;
        ll cnt = 14 - way;
        string temp = "";
        while(cnt)
        {
            if(cnt & 1) temp = "1" + temp;
            else temp = "0" + temp;
            cnt >>= 1;
        }
        while(temp.size() < 5) temp = "0" + temp;
        ans += temp;
        ans += string(now, way + 1, 10);
    }
    return ans;
}

ll string_to_ll(const string &s, int l = 1, int r = 5)
{
    ll ans = 0;
    for(int i=l; i<=r; i++)
        ans = ans * 2 + s[i] - '0';
    return ans;
}

double string_to_fl(string s)
{
    ll way = string_to_ll(s);
    double ans = 1, res = 1.0;
    for(int i=6; i<s.length(); i++)
    {
        res *= 0.5;
        ans += res * (s[i] - '0');
    }
    for(int i=way; i<15; i++) ans /= 2.0;
    for(int i=way; i>15; i--) ans *= 2.0;
    return ans;
}

double f16(double x)
{
    string now = fl_to_string(x);
    return string_to_fl(now);
}

int main()
{
    int t;
    cin >> t;
    while(t--)
    {
        int op;
        double a, b;
        cin >> op >> a >> b;
        if(op == 1) cout << fl_to_string(a) << "\n";
        else
        {
            double ans = 0;
            double aa = f16(a), bb = f16(b);
            if(op == 2) ans = aa + bb;
            else ans = aa * bb;
            cout << fl_to_string(ans) << "\n";
        }
    }
    return 0;
}