BZOJ3689 異或之

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我們需要知道一個事實，trie樹上是可以要求第k大的！

我們每個節點記個size值然後像其他資料結構一樣維護就可以了

然後我們再搞個priority_queue什麼的就好了，注意每個值會出現兩次只要記一次

 

  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 }

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(p.s. 注意會PE...然後改了一下輸出邊WA了QAQ...第三次才改對...)

BZOJ3689 異或之