I tried binary search, harsh table, got TLE. then I thought using direct mapping table could get MLE, but never TLE, so i tried it, still TLE!!!tell me how could this code get TLE.
#include <iostream>
using namespace std;
char a[1000000001];
int main()
{
    int n;
    cin >> n;
    for (int i = 1; i <= n; ++i) {
        int j;
        cin >> j;
        a[j] = 1;
    }
    int m;
    cin >> m;
    int cnt= 0;
    for (int i = 1; i <= m; ++i) {
        int j;
        cin >> j;
        cnt += a[j];
    }
    cout << cnt;
}

To start with, 1 billion might be a bit too huge of a number. Try 3 zeroes less maybe.

1) Try Visual C++ and c-style IO (printf/scanf)

2) http://acm.timus.ru/status.aspx?space=1&num=1196&author=184065 - run at 01:23:42
6 Oct 2016 - your program. MLE, as expected

Edited by author 06.10.2016 01:28

Insert this string:

int main()
{
  ios::sync_with_stdio(false); // It will speed up reading process
}

It doesn't (significantly) speed up Visual C++, as for me.
Using C-style IO (printf/scanf) is more predictable.