BZOJ3689 异或之

我们需要知道一个事实，trie树上是可以要求第k大的！

我们每个节点记个size值然后像其他数据结构一样维护就可以了

然后我们再搞个priority_queue什么的就好了，注意每个值会出现两次只要记一次

 /**************************************************************
     Problem: 3689
     User: rausen
     Language: C++
     Result: Accepted
     Time:4328 ms
     Memory:44524 kb
 ****************************************************************/

 #include <cstdio>
 #include <queue>

 using namespace std;
 const int N = 1e5 + ;
 const int Tot_sz = N * ;

 struct trie_node {
     trie_node *son[];
     int sz;
 } *null, *trie_root, mempool[Tot_sz], *cnt_trie = mempool;

 struct data {
     int x, y, k;
     data() {}
     data(int _x, int _y, int _k) : x(_x), y(_y), k(_k) {}

     inline bool operator < (const data &a) const {
         return x == a.x ? (y == a.y ? k > a.k : y > a.y) : x > a.x;
     }
 };

 int n, m;
 int a[N];
 priority_queue <data> h;

 inline int read() {
     int x = ;
     char ch = getchar();
     while (ch < '' || '' < ch)
         ch = getchar();
     while ('' <= ch && ch <= '') {
         x = x *  + ch - '';
         ch = getchar();
     }
     return x;
 }

 #define Son p -> son
 #define Sz p -> sz
 inline void trie_null(trie_node *&p) {
     p = cnt_trie;
     Son[] = Son[] = p;
     Sz = ;
 }

 inline void trie_new(trie_node *&p) {
     p = ++cnt_trie, *p = *null;
 }

 inline void trie_insert(int x) {
     static trie_node *p;
     static int i, t;
     for (p = trie_root, ++Sz, i = ; ~i; --i) {
         t = x >> i & ;
         if (Son[t] == null) trie_new(Son[t]);
         p = Son[t], ++Sz;
     }
 }

 inline int trie_query(int x, int rank) {
     static trie_node *p;
     static int i, t, res;
     for (p = trie_root, i = , res = ; ~i; --i) {
         t = x >> i & ;
         if (rank <= Son[t] -> sz) p = Son[t];
         else {
             rank -= Son[t] -> sz;
             res |=  << i;
             p = Son[!t];
         }
     }
     return res;
 }
 #undef Son
 #undef Sz

 int main() {
     int i, x, y, k;
     n = read(), m = read();
     trie_null(null);
     trie_new(trie_root);
     for (i = ; i <= n; ++i) {
         a[i] = read();
         trie_insert(a[i]);
     }
     for (i = ; i <= n; ++i)
         h.push(data(trie_query(a[i], ), a[i], ));
     for (i = ; i <  * m; ++i) {
         x = h.top().x, y = h.top().y, k = h.top().k;
         if (i & ) {
             if (i != ) putchar(' ');
             printf("%d", x);
         }
         h.pop();
         h.push(data(trie_query(y, k + ), y, k + ));
     }
     return ;
 }

(p.s. 注意会PE...然后改了一下输出边WA了QAQ...第三次才改对...)