144. 最长异或值路径

https://www.acwing.com/problem/content/submission/code_detail/8019318/

AcWing/144/144.cpp

@@ -0,0 +1,68 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int n, u, v, w, a[100005], ans;
+vector<pair<int, int>> g[100005];
+
+struct node {
+    int size;
+    node* next[2];
+
+    ~node() {
+        for (auto& i : next) {
+            delete i;
+        }
+    }
+};
+
+void dfs(int u, int fa, int sum) {
+    a[u] = sum;
+    for (auto i : g[u]) {
+        if (i.first != fa) {
+            dfs(i.first, u, sum ^ i.second);
+        }
+    }
+}
+
+void insert(node* root, int x, int b) {
+    if (!x) {
+        root->size++;
+        return;
+    }
+    if (root->next[(x >> b) & 1] == nullptr) root->next[(x >> b) & 1] = new node();
+    insert(root->next[(x >> b) & 1], x - (((x >> b) & 1) << b), b - 1);
+}
+
+int query(node* root, int x) {
+    int res = 0;
+    for (int i = 31; i >= 0; i--) {
+        if (root == nullptr) break;
+        if (root->next[!((x >> i) & 1)] != nullptr) {
+            res += 1 << i;
+            root = root->next[!((x >> i) & 1)];
+        } else {
+            root = root->next[(x >> i) & 1];
+        }
+    }
+    return res;
+}
+
+int main() {
+    node* root = new node();
+    cin >> n;
+    for (int i = 1; i < n; i++) {
+        cin >> u >> v >> w;
+        g[u].push_back(make_pair(v, w));
+        g[v].push_back(make_pair(u, w));
+    }
+    dfs(0, -1, 0);
+    for (int i = 0; i < n; i++) {
+        insert(root, a[i], 31);
+    }
+    for (int i = 0; i < n; i++) {
+        ans = max(ans, query(root, a[i]));
+    }
+    cout << ans << endl;
+    return 0;
+}