https://www.acmicpc.net/problem/1764
#include <iostream>
#include <vector>
#include <string>
#include <map>
#include <algorithm>
using namespace std;
int main(void)
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int N, M;
cin >> N >> M;
vector<string> not_hear, not_see, not_hear_see;
int cnt = 0;
string tmp;
for (int i = 0; i < N; i++)
{
cin >> tmp;
not_hear.push_back(tmp);
}
sort(not_hear.begin(), not_hear.end());
for (int i = 0; i < M; i++)
{
cin >> tmp;
not_see.push_back(tmp);
}
int left_idx, right_idx, mid_idx;
for (int i = 0; i < M; i++)
{
left_idx = 0;
right_idx = not_hear.size();
string target = not_see[i];
while (left_idx <= right_idx)
{
mid_idx = (left_idx + right_idx) / 2;
if (not_hear[mid_idx] == target)
{
cnt++;
not_hear_see.push_back(target);
break;
}
else if (not_hear[mid_idx] > target)
{
right_idx = mid_idx - 1;
}
else
{
left_idx = mid_idx + 1;
}
}
}
sort(not_hear_see.begin(), not_hear_see.end());
cout << cnt << endl;
for (auto x : not_hear_see)
{
cout << x << endl;
}
return 0;
}