URAL 1880 Psych Up's Eigenvalues （技巧）

Psych Up's Eigenvalues

Time limit: 0.5 second

Memory limit: 64 MB

At one of the contests at the Petrozavodsk Training Camp, players of the Psych Up team quickly found the simple problem and Fedya sat at the computer. The solution was ready in five minutes. Without
spending time for testing, Fedya submitted it and in a few seconds got Time Limit Exceeded.

Fedya crumpled the problem statement and left the room slamming the door behind him. Things were going the wrong way and he needed to wind down. On his way to the restroom Fedya heard a conversation
of the contest authors. Pasha was discussing with his friend the solution of the problem for which Fedya had got TLE. Fedya could only discern the word “eigenvalues.”

Fedya thought about it and decided that he, for sure, had his eigenvalues. For example, the date of birth, the number of his apartment, the mark he had got at the latest exam, or the number of travels
to contests. But they had a team contest, so what was their team's eigenvalue? Of course, a number was a team's eigenvalue if it was an eigenvalue for each of its players. With these joyful thoughts Fedya returned to the contest room.

Input

The input data consist of three blocks two lines each. The first line of each block contains the number n of a player's eigenvalues (1 ≤ n ≤ 4 000). In the second line
you are given n distinct integers in ascending order, which are the eigenvalues. All the eigenvalues are positive integers not exceeding 109.

Output

Output the number of eigenvalues of the Psych Up team.

Sample

input	output
5 13 20 22 43 146 4 13 22 43 146 5 13 43 67 89 146	3

题意：找三个序列中都有的数的个数。

解析：由于数太大，所以不能直接开个数组去统计个数，但是可以用map建立从int到int的映射，这样就不用考虑数太大不能当下表统计的烦恼了。

AC代码：

#include <cstdio>
#include <map>
using namespace std;

map<int, int> a;

int main(){
    #ifdef sxk
        freopen("in.txt", "r", stdin);
    #endif //sxk

    int n, ans = 0, c;
    while(~scanf("%d", &n)){
        for(int i=0; i<n; i++){
            scanf("%d", &c);
            ans += ++a[c] == 3;        //统计出现的个数
        }
    }
    printf("%d\n", ans);
    return 0;
}