[HNOI2002]营业额统计(Splay模板)

本来一直嫌麻烦只写spaly，结果被模板题卡T了，只能写正版splay，然后发现原来挺好写的,而且快了好多QwQ。

思路：每次对a_i统计“最小波动值”的时候有两种情况，a_j>=a_i和a_j<a_i，取差值最小的一种。就是a_i的前驱和后继，可以用splay维护和查找。

代码：

  1 #include <cstdio>
  2 #include <cstring>
  3 #include <iostream>
  4 using namespace std;
  5 
  6 struct SplayNode {
  7 	SplayNode *fa, *son[2];
  8 	int weight;
  9 	SplayNode(SplayNode *f = NULL, int w = 0):fa(f), weight(w) {
 10 		son[0] = son[1] = NULL;
 11 	}
 12 }*root = NULL;
 13 
 14 void rotate(SplayNode*);
 15 void Splay(SplayNode*);
 16 SplayNode *insert(int);
 17 SplayNode *findPredecessor(SplayNode*);
 18 SplayNode *findSuccessor(SplayNode*);
 19 
 20 int main() {
 21 	int n, ans = 0;
 22 	scanf("%d", &n);
 23 	for (int i = 0; i < n; i++) {
 24 		int d;
 25 		scanf("%d", &d);
 26 		if (!root) {
 27 			ans = d;
 28 			root = new SplayNode(NULL, d);
 29 		}
 30 		else {
 31 			SplayNode *p = insert(d);
 32 			int min_d = 0x3f3f3f3f;
 33 			SplayNode *l = findPredecessor(p), *r = findSuccessor(p);
 34 			if (l) min_d = p->weight - l->weight;
 35 			if (r) min_d = min(min_d, r->weight - p->weight);
 36 			ans += min_d;
 37 			//printf("%d
", min_d);
 38 		}
 39 	}
 40 	printf("%d
", ans);
 41 	return 0;
 42 }
 43 
 44 void rotate(SplayNode *rt) {
 45 	int d = (rt->fa->son[0] == rt);
 46 	SplayNode *f = rt->fa, *s = rt->son[d];
 47 	f->son[d ^ 1] = s;
 48 	if (s) s->fa = f;
 49 	rt->son[d] = f;
 50 	if (f->fa) f->fa->son[f->fa->son[1] == f] = rt;
 51 	rt->fa = f->fa;
 52 	f->fa = rt;
 53 }
 54 
 55 void Splay(SplayNode *rt) {
 56 	while(rt->fa) {
 57 		if (!rt->fa->fa) rotate(rt);
 58 		else {
 59 			int d1 = (rt->fa->son[1] == rt), d2 = (rt->fa->fa->son[1] == rt->fa);
 60 			if (d1 == d2) {
 61 				rotate(rt->fa);
 62 				rotate(rt);
 63 			} else {
 64 				rotate(rt);
 65 				rotate(rt);
 66 			}
 67 		}
 68 	}
 69 	root = rt;
 70 }
 71 
 72 SplayNode *insert(int w) {
 73 	SplayNode *p = root;
 74 	while (1) {
 75 		int d = (w > p->weight);
 76 		if (!p->son[d])
 77 			return p->son[d] = new SplayNode(p, w);
 78 		p = p->son[d];
 79 	}
 80 }
 81 
 82 SplayNode *findPredecessor(SplayNode *rt) {
 83 	Splay(rt);
 84 	if (!rt->son[0]) return NULL;
 85 	SplayNode *p = rt->son[0];
 86 	while (p->son[1]) p = p->son[1];
 87 	return p;
 88 }
 89 
 90 SplayNode *findSuccessor(SplayNode *rt) {
 91 	Splay(rt);
 92 	if (!rt->son[1]) return NULL;
 93 	SplayNode *p = rt->son[1];
 94 	while (p->son[0]) p = p->son[0];
 95 	return p;
 96 }

AC代码