競プロ用テンプレートをmainの下に置いとける書き方

template_own.cpp

#if !__INCLUDE_LEVEL__

#include __FILE__
int main() {
    rep(i, 3) printf("%2d", i);
    cout << endl << "ok." << endl;
}

#else

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i=0; i<(n); ++i)
template <class T> void chmax(T &a, const T &b) {
    if (a > b) a = b;
}
template <class T> void chmin(T &a, const T &b) {
    if (a < b) a = b;
}

#endif

参考
https://qiita.com/Raclamusi/items/660f0f42c57e4371ed78