Uva-10763-foreign Exchange

UVA-10763Foreign Exchange Time Limit: 3000MS Memory Limit: Unknown 64bit IO Format: %lld &%llu Submit Status Description Problem E Foreign Exchange Input: standard input output: standard output Time Limit: 1 second Your Non-Profit organization (icore - international Confederation of Revolver E nthusiasts) coordinates a very successful foreign student exchange program. Over the last few years, demand have sky-rocketed and now your need assistance with your task. The program your organization runs works as Follows:all candidates is asked for their original location and the location They would like to go. The program works out only if every student have a suitable exchange partner. In the other words, if a student wants to go from a to B, there must is another student who wants to go from B to a. This is an easy task when the There were only about the candidates, however now there is up to 500000 candidates! Input The input file contains multiple cases. Each test case would consist of a line containing n -The number of candidates (1≤n≤500000), followed by n lines representing the exchange information for each candidate. Each of these lines would contain 2 integers, separated by a single space, representing the candidate ' s original L Ocation and the candidate ' s target location respectively. Locations is represented by nonnegative integer numbers. Assume that no candidate'll has his or hers original location being the same as his or hers target location as th Is would fall to the domestic exchange program. The input is terminated by a case where n = 0; This case is should not being processed. Output For each test case, print ' YES ' on a ' if there is a ' a ', ' exchange program to work out, Otherwis E print "NO". Sample input Output for sample input 10 1 2 2 1 3 4 4 3 100 200 200 100 57 2 2 57 1 2 2 1 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 0 YES NO Problem Setter:gilbert Lee, University of Alberta, Canada Source Root:: Competitive programming 3:the New Lower Bound of programming contests (Steven & Felix Halim):: Problem Solvi Ng Paradigms:: Greedy:: Involving sorting (Or the Input is already Sorted) Root:: AOAPC i:beginning algorithm Contests (Rujia Liu):: Volume 4. Algorithm Design Root:: Competitive programming 2:this increases the lower bound of programming contests. Again (Steven & Felix Halim):: Problem Solving Paradigms:: Greedy-standard Root:: Competitive programming:increasing The Lower Bound of programming contests (Steven & Felix Halim):: Chapter 3. Problem solving Paradigms:: Greedy Root:: AOAPC ii:beginning algorithm Contests (Second Edition) (Rujia Liu):: Chapter 5. C + + and STL:: Exercises Root:: AOAPC i:beginning Algorithm Contests--Training Guide (Rujia Liu):: Chapter 1. Algorithm Design:: Designing Efficient Algorithms:: Exercises:beginner

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AC Code:

#include <cstdio> #include <cstring>using namespace std; int g[1000][1000], n;int check () {    int i,j;    for (i=0;i<1000;i++) for        (j=0;j<1000;j++)            if (g[i][j]!=0)                return 0;    return 1;} int main () {    int i, J, u, V;    while (1)    {        scanf ("%d", &n);        if (n==0) break            ;        memset (g, 0, sizeof (g));        for (i=0;i<n;i++)        {            scanf ("%d%d", &u,&v);            g[u][v]++;            g[v][u]--;        }        if (check ())            printf ("yes\n");        else            printf ("no\n");    }    return 0;    }

Uva-10763-foreign Exchange