Tuenti Contest 4 (Pablo Moreno)

/*
    Author: Pablo Moreno Olalla
    Email address: darthbrevu@yahoo.es
*/
#include <set>
#include <cstdio>
#include <string>
#include <vector>
#include <fstream>
#include <sstream>
#include <iostream>
#include <algorithm>

using namespace std;

//There are two basic options: either the contents of the file are stored in memory, or it is parsed
//each time some data must be found.

//Both approaches are quite inefficient in some sense (space/speed), so I choose the spatially inefficient
//code, which is really easy! The program will still be a little heavy in terms of memory usage, which is
//actually not that much of a deal. Several Mb are more than enough.

class TaskData  {
public:
    unsigned long long myDuration;
    set<size_t> dependencies;
    long long totalDuration;    //-1 if not set.
};

//I'll use a mix of C and C++ syntaxes. That's how I feel the most comfortable.
bool readFile(const string &in,vector<TaskData> &out)   {
    ifstream ifs(in.c_str());
    if (!ifs.is_open()) return false;
    string tmp;
    //Read the number of tasks
    unsigned long long N;   //OK, 32 bits are enough for *this* case, but that won't *always* be true, right?
    do  {
        getline(ifs,tmp);
        if (ifs.fail()||ifs.eof())  {
            ifs.close();
            return false;
        }
    }   while (sscanf(tmp.c_str(),"%Lu",&N)!=1);
    out.resize(static_cast<size_t>(N));
    //Read the duration of each task.
    unsigned long long a,b;
    for (unsigned long long i=0;i<N;++i)    {
        do  {
            getline(ifs,tmp);
            if (ifs.fail()||ifs.eof())  {
                ifs.close();
                return false;
            }
        }   while (sscanf(tmp.c_str(),"%Lu,%Lu",&a,&b)!=2);
        if (a!=i)   {
            cout<<"Missing task "<<i<<'!'<<endl;
            ifs.close();
            return false;
        }
        out[i].myDuration=b;
        out[i].totalDuration=-1;
    }
    //Now read the dependencies.
    for (;;)    {
        getline(ifs,tmp);
        if (ifs.eof())  {
            ifs.close();
            return true;
        }   else if (ifs.fail())    {
            ifs.close();
            return false;
        }
        istringstream iss(tmp);
        iss>>a;
        if (iss.fail()) continue;
        for (;;)    {
            iss.ignore(1);  //The comma.
            iss>>b;
            if (iss.fail()) break;
            else out[a].dependencies.insert(b);
        }
    }
}

unsigned long long getDuration(vector<TaskData> &data,size_t i) {
    TaskData &td=data[i];
    if (td.totalDuration>=0) return static_cast<unsigned long long>(td.totalDuration);
    unsigned long long maxN=0;
    set<size_t>::const_iterator end=td.dependencies.end();
    for (set<size_t>::const_iterator it=td.dependencies.begin();it!=end;++it) maxN=max(maxN,getDuration(data,*it));
    return td.totalDuration=td.myDuration+maxN;
}

int main(int argc,char **argv)  {
    string fn;
    fn=((argc<=1)?"in":string(argv[1]));
    //The following two lines are not strictly necessary, but make the code a little more handy.
    if (argc>=3) freopen(argv[2],"r",stdin);
    if (argc>=4) freopen(argv[3],"w",stdout);
    vector<TaskData> data(0);
    if (!readFile(fn,data)) return -1;  //Couldn't read file.
    size_t i;
    cin>>i;
    if (!cin.fail()&&i<data.size()) cout<<i<<' '<<getDuration(data,i)<<endl;
    do  {
        cin.ignore(1);  //skip commas.
        cin>>i;
        if (!cin.fail()&&i<data.size()) cout<<i<<' '<<getDuration(data,i)<<endl;
        else break;
    }   while (!cin.eof());
    return 0;
}