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B - Bitwise Exclusive-OR Sequence
https://codeforces.com/gym/103427/submission/176125289
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Gym/103427/B/B.cpp
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78
Gym/103427/B/B.cpp
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#include <iostream>
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#include <utility>
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#include <vector>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = 1e5 + 5;
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int n, m, w[N << 1], cnt[2];
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long long ans;
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bool v[N << 1], vis[N], now[N];
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std::vector<std::pair<int, int>> g[N];
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void dfs(int u) {
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vis[u] = true;
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cnt[now[u]]++;
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for (auto e : g[u]) {
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int v = e.first,
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id = e.second;
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if (vis[v]) {
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if (now[u] ^ now[v] != ::v[id]) {
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cout << -1 << endl;
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exit(0);
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}
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continue;
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}
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now[v] = now[u] ^ ::v[id];
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dfs(v);
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}
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}
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int main() {
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std::ios::sync_with_stdio(false);
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cin.tie(nullptr);
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cin >> n >> m;
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for (int i = 1, u, v; i <= m; i++) {
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cin >> u >> v >> w[i];
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g[u].emplace_back(v, i);
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g[v].emplace_back(u, i);
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}
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for (int k = 0; k < 30; k++) {
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int res = 0;
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std::fill_n(vis, N, false);
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std::fill_n(now, N, false);
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for (int i = 1; i <= m; i++) {
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v[i] = (w[i] >> k) & 1;
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}
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for (int i = 1; i <= n; i++) {
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if (!vis[i]) {
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cnt[0] = cnt[1] = 0;
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dfs(i);
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res += std::min(cnt[0], cnt[1]);
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}
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}
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ans += static_cast<long long>(1 << k) * res;
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}
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cout << ans << endl;
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return 0;
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}
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