UVA10763 Foreign Exchange[map+배열]

Your non-profit organization (iCORE - international Confederation of Revolver Enthusiasts) coordinates a very successful foreign student exchange program. Over the last few years, demand has sky-rocketed and now you need assistance with your task.
  The program your organization runs works as follows: All candidates are asked for their original location and the location they would like to go to. The program works out only if every student has a suitable exchange partner. In other words, if a student wants to go from A to B, there must be another student who wants to go from B to A. This was an easy task when there were only about 50 candidates, however now there are up to 500000 candidates!
Input
The input file contains multiple cases. Each test case will 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 will contain 2 integers, separated by a single space, representing the candidate's original location and the candidate’s target location respectively. Locations will be represented by nonnegative integer numbers. You may assume that no candidate will have his or her original location being the same as his or her target location as this would fall into the domestic exchange program. The input is terminated by a case where n = 0; this case should not be processed.
Output
For each test case, print ‘YES’ on a single line if there is a way for the exchange program to work out, otherwise print ‘NO’.
Sample Input
십
1 2
2 1
3 4
4 3
100 200
200 100
57 2
2 57
1 2
2 1
십
1 2
3 4
5 6
7 8
9 10
11 12
13 14
15 16
17 18
19 20
0
Sample Output
YES
NO
문제 링크: UVA10763 Foreign Exchange
질문 요약: (약관)
문제 분석:
여기서 두 가지 해법을 제시한다. 첫째, 맵을 이용하여 통계의 정과 음 통계를 하고 통계 결과가 0으로 변하면 교환할 수 있고 0으로 변하지 않으면 교환할 수 없다.둘째, 수조를 사용하여 시뮬레이션 교환을 하고 다시 바꾸면 교환할 수 있다는 뜻이다.
프로그램 설명: (약관)
제목: (약간)
참조 링크: (약관)
AC의 C++ 언어 프로그램은 다음과 같습니다.

/* UVA10763 Foreign Exchange */

#include 

using namespace std;

const int N = 5e5;
int ex[N + 1];

void init()
{
    for(int i=0; i

AC의 C++ 언어 프로그램은 다음과 같습니다.

/* UVA10763 Foreign Exchange */

#include 

using namespace std;

int main()
{
    int n;
    while(~scanf("%d", &n) && n) {
        map m;

        for(int i=1; i<=n; i++) {
            int a, b;
            scanf("%d%d", &a, &b);

            m[a]++;
            m[b]--;
        }

        bool ans = true;
        for(const auto &r : m)
            if(r.second) {
                ans = false;
                break;
            }

        printf("%s
", ans ? "YES" : "NO");
    }

    return 0;
}