#3048. 「十二省联考 2019」异或粽子

https://loj.ac/s/1651495

LibreOJ/3048/3048.cpp

@@ -0,0 +1,125 @@
+#include <iostream>
+#include <functional>
+#include <numeric>
+#include <queue>
+#include <tuple>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 5e5 + 5;
+
+class Trie {
+  private:
+    const int len = 30;
+
+    struct node {
+        int cnt;
+        node* child[2];
+
+        node()
+            : cnt(0), child{0, 0} {}
+
+        ~node() {
+            if (child[0]) delete child[0];
+            if (child[1]) delete child[1];
+        }
+    };
+
+    node* root;
+
+  public:
+    Trie()
+        : root(new node()) {}
+
+    ~Trie() {
+        delete root;
+    }
+
+    void insert(unsigned long long val) {
+        node* cur = root;
+
+        cur->cnt++;
+
+        for (int i = 32; ~i; i--) {
+            bool x = (val >> i) & 1;
+
+            if (cur->child[x] == nullptr) cur->child[x] = new node();
+
+            cur = cur->child[x];
+            cur->cnt++;
+        }
+    }
+
+    unsigned long long query(unsigned long long val, int k) {
+        node* cur = root;
+        unsigned long long res = 0;
+
+        for (int i = 32; ~i; i--) {
+            bool x = (val >> i) & 1;
+
+            if (cur->child[x] && cur->child[x]->cnt >= k) {
+                cur = cur->child[x];
+            } else {
+                if (cur->child[x]) k -= cur->child[x]->cnt;
+                cur = cur->child[x ^ 1];
+                res |= 1ll << i;
+            }
+        }
+
+        return res;
+    }
+};
+
+int n, k;
+unsigned long long s[N], ans;
+std::priority_queue<
+    std::tuple<int, int, unsigned long long>,
+    std::vector<std::tuple<int, int, unsigned long long>>,
+    auto(*)(std::tuple<int, int, unsigned long long>, std::tuple<int, int, unsigned long long>)->bool>
+    q{[](std::tuple<int, int, unsigned long long> lhs, std::tuple<int, int, unsigned long long> rhs) -> bool {
+        return std::get<2>(lhs) < std::get<2>(rhs);
+    }};
+Trie trie;
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> k;
+
+    k <<= 1;
+    trie.insert(0);
+
+    for (int i = 1; i <= n; i++) {
+        unsigned long long x;
+
+        cin >> x;
+
+        s[i] = s[i - 1] ^ x;
+        trie.insert(s[i]);
+    }
+
+    for (int i = 0; i <= n; i++) {
+        q.emplace(i, n + 1, trie.query(s[i], n + 1));
+    }
+
+    while (k--) {
+        auto t = q.top();
+        q.pop();
+
+        ans += std::get<2>(t);
+
+        if (std::get<1>(t)) {
+            q.emplace(
+                std::get<0>(t),
+                std::get<1>(t) - 1,
+                trie.query(s[std::get<0>(t)], std::get<1>(t) - 1));
+        }
+    }
+
+    cout << (ans >> 1) << endl;
+
+    return 0;
+}