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OI-codes/Luogu/P6824/P6824.cpp

55 lines
1.1 KiB
C++

#include <bits/stdc++.h>
using namespace std;
int n, k, a[1000005], ans;
struct node {
int val;
node* next[2];
~node() {
for (auto& i : next) {
delete i;
}
}
};
void insert(node* root, int x) {
for (int i = 21; i >= 0; i--) {
if (root->next[(x >> i) & 1] == nullptr) root->next[(x >> i) & 1] = new node();
root = root->next[(x >> i) & 1];
root->val++;
}
}
int search(node* root, int x) {
int res = 0;
node* p = root;
for (int i = 21; i >= 0; i--) {
int c = (x >> i) & 1;
int t = (k >> i) & 1;
if (t && p->next[1 - (c ^ t)] != nullptr) {
res += p->next[1 - (c ^ t)]->val;
}
if (p->next[c ^ t] == nullptr) break;
p = p->next[c ^ t];
}
return res;
}
int main() {
node* root = new node();
cin >> n >> k;
for (int i = 0; i < n; i++) {
cin >> a[i];
insert(root, a[i]);
}
for (int i = 0; i <= 2097151; i++) {
ans = max(ans, search(root, i));
}
cout << ans << endl;
delete root;
return 0;
}