The Trip PC/UVa IDs: 110103/10137, Popularity: B, Success rate: average Level: 1

#include<cstdio>
#include<iostream>
#include<string>
#include<algorithm>
#include<iterator>

using namespace std;
/*
* A solution for "The Trip" problem.
* UVa ID: 10137
*/
#include <stdio.h>

int main (int argc, const char * argv[]) {
    /* number of students in the trip */
    long numOfStudents;
   
    /* the total sum of money spent */
    double total;
   
    /* the total amount of money to exchange in order to equalize */
    double exchange;
   
    /* the equalized trip amount to be payed by each student */
    double equalizedAmount;
   
    /* difference between the equalized amount and the amount spent */
    double diff;
   
    /* sum of all negative differences */
    double negativeSum;
   
    /* sum of all positive differences */
    double positiveSum;
   
    /* iterator */
    int i;
   
    while(scanf("%ld", &numOfStudents) != EOF) {
               
        /* 0, ends the program */
        if (!numOfStudents) {
            return 0;
        }
       
        /* keeps the amount of money spent by each student */
        double amountSpent[numOfStudents];     
       
        /* clean */
        total = 0;
        negativeSum = 0;
        positiveSum = 0;
               
        for (i = 0; i < numOfStudents; i++) {
            scanf("%lf\n", &amountSpent[i]);
            total += amountSpent[i];
        }
               
        equalizedAmount = total / numOfStudents;
       
        for (i = 0; i < numOfStudents; i++) {
            /* to ensure 0.01 precision */
            diff = (double) (long) ((amountSpent[i] - equalizedAmount) * 100.0) / 100.0;
           
            if (diff < 0) {
                negativeSum += diff;
            } else {
                positiveSum += diff;
            }
        }

        /* when the total amount is even, these sums do not differ. otherwise, they differ in one cent */
        exchange = (-negativeSum > positiveSum) ? -negativeSum : positiveSum;
                       
        /* output result */
        printf("$%.2lf\n", exchange);
    }

    return 0;
}