Submission #1867229

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Source Code Expand

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

vector<int> G[100010];
int id[100010];

bool check(int u, int f) {
  if (id[u]) return id[u] == f;
  id[u] = f;
  bool res = true;
  for (int i = 0; i < G[u].size(); i++) {
    res &= check(G[u][i], (f > 0 ? -1 : 1));
  }
  return res;
}

int main(void) {
  ll n, m;
  cin >> n >> m;
  for (int i = 0; i < m; i++) {
    int a, b;
    cin >> a >> b;
    a--, b--;
    G[a].push_back(b);
    G[b].push_back(a);
  }

  if (check(0, 1)) {
    ll b = 0, w = 0;
    for (int i = 0; i < n; i++) {
      b += id[i] == 1;
      w += id[i] == -1;
    }
    cout << b * w - m << endl;
  } else {
    cout << n * (n - 1) / 2 - m << endl;
  }

  return 0;
}

Submission Info

Judge Result