Submission #23504857

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;

struct Unionfind {
  // tree number
  vector<int> par;
  // constructor
  Unionfind(int n = 1) : par(n, -1) {}
  // search root
  int root(int x) {
    if (par[x] < 0) return x;
    return par[x] = root(par[x]);
  }
  // is same?
  bool issame(int x, int y) { return root(x) == root(y); }

  // add
  // already added, return 0
  bool uni(int x, int y) {
    x = root(x);
    y = root(y);
    if (x == y) return 0;
    if (par[x] > par[y]) swap(x, y);
    par[x] += par[y];
    par[y] = x;
    return 1;
  }
  int size(int x) { return -par[root(x)]; }
};

using P = pair<int, int>;

int n, m;
set<int> a;

vector<P> solve();

int main() {
  cin >> n >> m;
  {
    for (int i = 1; i < n; ++i) a.insert(i);
    for (int i = 0; i < m; ++i) {
      int p;
      cin >> p;
      a.erase(p);
    }
  }
  auto res = solve();
  if (res.size() == n - 1)
    for (auto [x, y] : res) cout << x << " " << y << endl;
  else
    cout << -1 << endl;
  return 0;
}

vector<P> solve() {
  vector<P> res;
  vector<int> base, v;
  for (auto p : a) {
    int x = p;
    for (auto q : base) p = min(p, p ^ q);
    if (p) {
      base.push_back(p);
      v.push_back(x);
    }
  }
  Unionfind uf(n);
  for (int p = 0; p < n; ++p)
    for (auto q : v)
      if (!uf.issame(p, p ^ q)) {
        uf.uni(p, p ^ q);
        res.emplace_back(p, p ^ q);
      }
  return res;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:49:18: warning: comparison of integer expressions of different signedness: ‘std::vector<std::pair<int, int> >::size_type’ {aka ‘long unsigned int’} and ‘int’ [-Wsign-compare]
   49 |   if (res.size() == n - 1)
      |       ~~~~~~~~~~~^~~~~~~~

Judge Result