USACO-T039: Fractions to Decimals

/*
ID: mickyta1
TASK: fracdec
LANG: C++
*/

#include <bits/stdc++.h>
using namespace std;

#define f first
#define s second
typedef pair<int, int> pii;

const int N = 1e5 + 5;

deque<pii> cycle;
vector<pii> noCycle;
string str;
bool visited[N];

void printStr(){
    int upb = ((int)str.size() + 75) / 76;
    for(int i = 0; i < upb; ++i){
        for(int j = 0; j < 76 && 76 * i + j < str.size(); ++j){
            cout << str[76 * i + j];
        }
        cout << '\n';
    }
}

int main(){
    freopen("fracdec.in", "r", stdin);
    freopen("fracdec.out", "w", stdout);

    int st, deno;
    scanf("%d%d", &st, &deno);
    if(st % deno == 0){
        cout << st / deno << ".0\n";
        fclose(stdin);
        fclose(stdout);
        return 0;
    }
    str += to_string(st / deno);
    str.push_back('.');
    st %= deno;
    while(true){
        if(st == 0){
            goto hasNoCycle;
        }
        int u = 10 * st / deno;
        if(visited[st]){
            while(!cycle.empty() && cycle.front().s != st){
                noCycle.push_back(cycle.front());
                cycle.pop_front();
            }
            goto hasCycle;
        }
        visited[st] = true;
        cycle.emplace_back(u, st);
        st = 10 * st % deno;
    }
hasNoCycle:
    for(int i = 0; i < cycle.size(); ++i){
        str.push_back((char)(cycle[i].f + '0'));
    }
    printStr();
    fclose(stdin);
    fclose(stdout);
    return 0;
hasCycle:
    for(int i = 0; i < noCycle.size(); ++i){
        str.push_back((char)(noCycle[i].f + '0'));
    }
    str.push_back('(');
    for(int i = 0; i < cycle.size(); ++i){
        str.push_back((char)(cycle[i].f + '0'));
    }
    str.push_back(')');
    printStr();
    fclose(stdin);
    fclose(stdout);
    return 0;
}