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
1 /************************************************************** 2 Problem: 3689 3 User: rausen 4 Language: C++ 5 Result: Accepted 6 Time:4328 ms 7 Memory:44524 kb 8 ****************************************************************/ 9 10 #include <cstdio> 11 #include <queue> 12 13 using namespace std; 14 const int N = 1e5 + 5; 15 const int Tot_sz = N * 35; 16 17 struct trie_node { 18 trie_node *son[2]; 19 int sz; 20 } *null, *trie_root, mempool[Tot_sz], *cnt_trie = mempool; 21 22 struct data { 23 int x, y, k; 24 data() {} 25 data(int _x, int _y, int _k) : x(_x), y(_y), k(_k) {} 26 27 inline bool operator < (const data &a) const { 28 return x == a.x ? (y == a.y ? k > a.k : y > a.y) : x > a.x; 29 } 30 }; 31 32 int n, m; 33 int a[N]; 34 priority_queue <data> h; 35 36 inline int read() { 37 int x = 0; 38 char ch = getchar(); 39 while (ch < '0' || '9' < ch) 40 ch = getchar(); 41 while ('0' <= ch && ch <= '9') { 42 x = x * 10 + ch - '0'; 43 ch = getchar(); 44 } 45 return x; 46 } 47 48 #define Son p -> son 49 #define Sz p -> sz 50 inline void trie_null(trie_node *&p) { 51 p = cnt_trie; 52 Son[0] = Son[1] = p; 53 Sz = 0; 54 } 55 56 inline void trie_new(trie_node *&p) { 57 p = ++cnt_trie, *p = *null; 58 } 59 60 inline void trie_insert(int x) { 61 static trie_node *p; 62 static int i, t; 63 for (p = trie_root, ++Sz, i = 30; ~i; --i) { 64 t = x >> i & 1; 65 if (Son[t] == null) trie_new(Son[t]); 66 p = Son[t], ++Sz; 67 } 68 } 69 70 inline int trie_query(int x, int rank) { 71 static trie_node *p; 72 static int i, t, res; 73 for (p = trie_root, i = 30, res = 0; ~i; --i) { 74 t = x >> i & 1; 75 if (rank <= Son[t] -> sz) p = Son[t]; 76 else { 77 rank -= Son[t] -> sz; 78 res |= 1 << i; 79 p = Son[!t]; 80 } 81 } 82 return res; 83 } 84 #undef Son 85 #undef Sz 86 87 int main() { 88 int i, x, y, k; 89 n = read(), m = read(); 90 trie_null(null); 91 trie_new(trie_root); 92 for (i = 1; i <= n; ++i) { 93 a[i] = read(); 94 trie_insert(a[i]); 95 } 96 for (i = 1; i <= n; ++i) 97 h.push(data(trie_query(a[i], 2), a[i], 2)); 98 for (i = 1; i < 2 * m; ++i) { 99 x = h.top().x, y = h.top().y, k = h.top().k; 100 if (i & 1) { 101 if (i != 1) putchar(' '); 102 printf("%d", x); 103 } 104 h.pop(); 105 h.push(data(trie_query(y, k + 1), y, k + 1)); 106 } 107 return 0; 108 }
(p.s. 注意会PE...然后改了一下输出边WA了QAQ...第三次才改对...)