提升C++输入输出性能

做题的时候，由于数据量大，很多情况下得用scanf和printf代替cin和cout用于输入输出。难道C++不行么？

百度了一下，有三条建议用于提高C++的输入输出速度：

• At the first line in main function,add :std::ios_base::sync_with_stdio(false).which cancel theSynchronization between <iostream> and <cstdio>;
• At the second line in main function,add: std::cin.tie(0).which leads to that cin ties nothing.cin ties cout at first.
• For all endl, use ‘\n’ or”\n” instead.

#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
int main()
{
    std::ios::sync_with_stdio(false);
    cin.tie(0);
    int n,m;
    cin>>n>>m;
    cout<<n<<" "<<m<<"\n";
    return 0;
}