2972. 分数的精确值

#include <cstdint>
#include <iostream>
#include <unordered_map>

int main() {
    using u32 = uint32_t;
    u32 t;
    std::cin >> t;
    for (u32 i = 0; i != t; ++i) {
        u32 n, m;
        std::cin >> n >> m;
        std::cout << "case #" << i << ":\n" << n / m;
        n = n % m * 10;
        if (!n) {
            std::cout << '\n';
            continue;
        }
        std::cout << '.';
        using BitPos = u32;
        using Dividend = u32;
        u32 bit_cnt = 1;
        std::unordered_map<Dividend, BitPos> table{{n, bit_cnt}};
        do {
            std::cout << n / m;
            n = n % m * 10;
            if (auto [it, ok] = table.insert({n, bit_cnt += 1}); !ok) {
                std::cout << '\n' << it->second << '-' << bit_cnt - 1;
                break;
            }
        } while (n);
        std::cout << '\n';
    }
}

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main()
{
    int T;
    cin >> T;
    for (int cse = 0; cse < T; cse++)
    {
        cout << "case #" << cse << ":" << endl;
        int a, b;
        cin >> a >> b;
        vector<int> R; // 余数
        vector<int> Q; // 商
        int z = a / b; // 整数部分
        cout << z << ".";
        a %= b;
        bool inf = false;
        int begini,endi; //循环节开始和结束位
        for(;;)
        {
            a *= 10;
            int q = a / b;
            int r = a % b;
            a = r;            
            if (r == 0)
            {
                Q.push_back(q);
                inf = false;
                break;
            }
            else
            {
                vector<int>::iterator it = find(R.begin(), R.end(), r);
                if (it == R.end()) // 余数不重复
                {
                    Q.push_back(q);
                    R.push_back(r);
                }
                else // 余数重复
                {
                    begini = it - R.begin(); // 这里是算的索引值，后面输出要 +1
                    inf = true;
                    if (q != Q[begini]) // 起初就是因为少了这个判断和 +1 的逻辑，试了很多次，样例都过不了
                    {
                        begini++; 
                        Q.push_back(q); // 前面不相等的商不是循环节，因此要把这个商放进去
                    }
                    endi = Q.size(); 
                    break;
                }

            }

        }
        for (int i = 0; i < Q.size(); i++)
        {
            cout << Q[i];
        }
        cout << endl;
        if (inf)
        {
            cout << (begini + 1) << '-' << endi << endl;
        }
    }
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
void solve()
{
    int n,m;
    cin>>n>>m;
    int ans[10000],rmdr[10000];
    int k=0,j=0,flag=0;
    int intpart=n/m;
    rmdr[j++]=n%m;
    n%=m;
    cout<<intpart<<'.';
    while(n%m!=0)
    {
        n*=10;
        ans[k]=n/m;
        rmdr[j++]=n%m;
        n%=m;
        cout<<ans[k++];
        for(int i=0;i<j-1;i++)
        {
            if(rmdr[i]==rmdr[j-1])
            {
                flag=1;
                if(i==j-2)
                {
                    cout<<endl<<i+1<<'-'<<i+1<<endl;
                    break;
                }
                else
                {
                    cout<<endl<<i+1<<'-'<<j-1<<endl;
                    break;
                }
            }
        }
        if(flag==1)
            break;
    }
    if(flag==0)
        cout<<endl;

}
int main()
{
    int T;
    cin>>T;
    for(int i=0;i<T;i++)
    {
        printf("case #%d:\n",i);
        solve();
    }
    return 0;
}

import re
from decimal import *

getcontext().prec = 2077
for _ in range(int(input())):
    print(f'case #{_}:')
    a, b = map(Decimal, input().split())
    s = str(a / b)
    m = re.search(r'(.+?)(?=\1{10,})', s)
    if m:
        print(s[:m.end()])
        print(f'{m.start() - 1}-{m.end() - 2}')
    else:
        print(s)