Greedy Gift Givers

A group of NP (2 ≤ NP ≤ 10) uniquely named friends has decided to exchange gifts of money. Each of these friends might or might not give some money to any or all of the other friends. Likewise, each friend might or might not receive money from any or all of the other friends. Your goal in this problem is to deduce how much more money each person gives than they receive.

The rules for gift-giving are potentially different than you might expect. Each person sets aside a certain amount of money to give and divides this money evenly among all those to whom he or she is giving a gift. No fractional money is available, so dividing 3 among 2 friends would be 1 each for the friends with 1 left over -- that 1 left over stays in the giver's "account".

In any group of friends, some people are more giving than others (or at least may have more acquaintances) and some people have more money than others.

Given a group of friends, no one of whom has a name longer than 14 characters, the money each person in the group spends on gifts, and a (sub)list of friends to whom each person gives gifts, determine how much more (or less) each person in the group gives than they receive.

IMPORTANT NOTE

The grader machine is a Linux machine that uses standard Unix conventions: end of line is a single character often known as '\n'. This differs from Windows, which ends lines with two charcters, '\n' and '\r'. Do not let your program get trapped by this!

PROGRAM NAME: gift1

INPUT FORMAT

SAMPLE INPUT (file gift1.in)

5

dave

laura

owen

vick

amr

dave

200 3

laura

owen

vick

owen

500 1

dave

amr

150 2

vick

owen

laura

0 2

amr

vick

vick

0 0

OUTPUT FORMAT

The output is NP lines, each with the name of a person followed by a single blank followed by the net gain or loss (final_money_value - initial_money_value) for that person. The names should be printed in the same order they appear on line 2 of the input.

All gifts are integers. Each person gives the same integer amount of money to each friend to whom any money is given, and gives as much as possible that meets this constraint. Any money not given is kept by the giver.

SAMPLE OUTPUT (file gift1.out)

dave 302

laura 66

owen -359

vick 141

My Answer:

/*

ID: horisly1

PROG: gift1

LANG: C++

*/

#include <iostream>

#include <fstream>

#include <string>

#include <vector>

#include <map>

using namespace std;

class Friend {

private:

    string m_sName;

    int m_nMoney;

    int m_nPerGift;

    int m_nFriends;

    int m_nTotalRecGift;

    int m_nTotalGiveGift;

public:

    Friend(string name):m_sName(name),m_nMoney(0),m_nFriends(0),m_nTotalRecGift(0),m_nTotalGiveGift(0) { }

    void SetMoney(int money) {

        m_nMoney = money;

    }

    void SetFriends(int n) {

        m_nFriends = n;

    }

    void RecGift(int gift) {

        m_nTotalRecGift += gift;

    }

    int GiveGift() {

        if( m_nFriends == 0 || m_nMoney == 0 )

                m_nPerGift = 0;

        else {

                m_nPerGift = m_nMoney / m_nFriends;

                m_nTotalGiveGift = m_nPerGift * m_nFriends;

        }

        return m_nPerGift;

    }

    int GetTotalGiveGift() {

        return m_nTotalGiveGift;

    }

    int GetTotalRecGift() {

        return m_nTotalRecGift;

    }

};

int main() {

    ifstream fin ("gift1.in");

    ofstream fout ("gift1.out");

    int NP;

    fin >> NP;

    map<string,Friend> npMap;

    vector<string> vName;

    for(int i=0; i<NP; i++) {

        string name;

        fin >> name; 

        vName.push_back(name);

        Friend f(name);

        npMap.insert(make_pair(name,f));

    }

    map<string,Friend>::iterator pos;

    for(int k=0; k<NP; k++) {

        string szName;

        fin >> szName;

        pos = npMap.find(szName);

        int money, n;

        string szFriend;

        fin >> money >> n;               

        pos->second.SetMoney(money);

        pos->second.SetFriends(n);

        int gift = pos->second.GiveGift();

        map<string,Friend>::iterator p;

        for(int i=0; i<n; i++) {

                fin >> szFriend;

                p = npMap.find(szFriend);

                p->second.RecGift(gift);

        }

    }

    for(int i=0; i<NP; i++) {

        string name = vName[i];

        map<string,Friend>::iterator p;

        p = npMap.find(name);

        int banlance = p->second.GetTotalRecGift() - p->second.GetTotalGiveGift();

        fout << p->first << " " << banlance <<endl;

    }

    return 0;

}

The Answer of the website:

The hardest part about this problem is dealing with the strings representing people's names.

We keep an array of Person structures that contain their name and how much money they give/get.

The heart of the program is the lookup() function that, given a person's name, returns their Person structure. We add new people with addperson().

Note that we assume names are reasonably short.

#include <stdio.h>

#include <string.h>

#include <assert.h>

#define MAXPEOPLE 10

#define NAMELEN           32

typedef struct Person Person;

struct Person {

    char name[NAMELEN];

    int total;

};

Person people[MAXPEOPLE];

int npeople;

void

addperson(char *name)

{

    assert(npeople < MAXPEOPLE);

               strcpy(people[npeople].name, name);

    npeople++;

}

Person*

lookup(char *name)

{

    int i;

    /* look for name in people table */

    for(i=0; i<npeople; i++)

               if(strcmp(name, people[i].name) == 0)

                   return &people[i];

    assert(0);      /* should have found name */

}

int

main(void)

{

    char name[NAMELEN];

    FILE *fin, *fout;

    int i, j, np, amt, ng;

    Person *giver, *receiver;

    fin = fopen("gift1.in", "r");

    fout = fopen("gift1.out", "w");

    fscanf(fin, "%d", &np);

    assert(np <= MAXPEOPLE);

    for(i=0; i<np; i++) {

               fscanf(fin, "%s", name);

               addperson(name);

    }

    /* process gift lines */

    for(i=0; i<np; i++) {

               fscanf(fin, "%s %d %d", name, &amt, &ng);

               giver = lookup(name);

               for(j=0; j<ng; j++) {

                   fscanf(fin, "%s", name);

                   receiver = lookup(name);

                   giver->total -= amt/ng;

                   receiver->total += amt/ng;

               }

    }

    /* print gift totals */

    for(i=0; i<np; i++)

               printf("%s %d\n", people[i].name, people[i].total);

    exit (0);

}