B - Bitwise Exclusive-OR Sequence

https://codeforces.com/gym/103427/submission/176125289

Gym/103427/B/B.cpp

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