点 p1 と点 p2 を使った正方形の座標（p3, p4）を返す

#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using P = pair<int, int>;
#define rep(i, n) for(int i = 0; i < (n); ++i)
// using mint = modint998244353;
// using mint = modint1000000007;
// const int mod = 1000000007;
// const ll INF = 1LL << 62;
// const int INF = 1001001001;

/**
 * 点 p1 と点 p2 を使った正方形の座標（p3, p4）を返す
 * 前提 : p1 != p2
 */
vector<P> calcSquareUsingPoints(P p1, P p2) {
  int dy = p2.first - p1.first;
  int dx = p2.second - p1.second;
  int y3 = p2.first + dx;
  int x3 = p2.second - dy;
  int y4 = y3 - dy;
  int x4 = x3 - dx;

  vector<P> res;
  res.push_back(make_pair(y3, x3));
  res.push_back(make_pair(y4, x4));
  return res;
}

int main() {
  rep(y1, 9) {
    rep(x1, 9) {
      rep(y2, 9) {
        rep(x2, 9) {
          if(y1 == y2 && x1 == x2) { continue; }
          vector<P> res = calcSquareUsingPoints(make_pair(y1, x1), make_pair(y2, x2));

          int y3 = res[0].first;
          int x3 = res[0].second;
          int y4 = res[1].first;
          int x4 = res[1].second;

          cout << y1 << "," << x1 << " ";
          cout << y2 << "," << x2 << " ";
          cout << y3 << "," << x3 << " ";
          cout << y4 << "," << x4 << endl;
        }
      }
    }
  }

  return 0;
}