HNOI2002营业额统计

 1 #include <cstdio>
 2 #include <cstdlib>
 3 #include <ctime>
 4 using namespace std;
 5 const int inf=10000000;
 6 struct node{
 7     int val,weight;
 8     node *ch[2];
 9     node (int key) {
10         val=key;weight=rand();
11         ch[0]=ch[1]=NULL;
12     }
13 }*root;
14 int n,ans;
15 void rotate(node *&t,int d){
16     node *c=t->ch[d];
17     t->ch[d]=c->ch[!d];
18     c->ch[!d]=t;
19     t=c;
20 }
21 bool find (node *t,int key){
22     while (t!=NULL) {
23         if (t->val==key) return 1;
24         t=t->ch[key>(t->val)];
25     }
26     return 0;    
27 }
28 int pred (node *t,int key){
29     int ret=-inf;
30     while (t!=NULL) {
31         if (t->val<key) {if (t->val>ret) ret=t->val;t=t->ch[1];} else 
32             t=t->ch[0];
33     }
34     return ret;
35 }
36 int succ (node *t,int key){
37     int ret=inf;
38     while (t!=NULL) {
39         if (t->val>key) {if (t->val<ret) ret=t->val;t=t->ch[0];} else 
40             t=t->ch[1];    
41     }
42     return ret;
43 }
44 void insert (node *&t,int key){
45     if (t==NULL) {
46         t=new node(key);return ;
47     }    
48     int d=key>t->val;
49     insert(t->ch[d],key);
50     if (t->ch[d]->weight>t->weight) rotate(t,d);
51 }
52 int main(){
53     ans=0;
54     srand(19961111);
55     scanf("%d",&n);
56     int x,x1,x2;
57     scanf("%d",&x);ans+=x;
58     root=new node(x);
59     for (int i=2;i<=n;i++){
60         if (scanf("%d",&x)==EOF) x=0;
61         if (!find(root,x)) {
62             x1=pred(root,x);x2=succ(root,x);
63             ans+=(x2-x<x-x1)?x2-x:x-x1;
64             insert(root,x);
65         }
66     }
67     printf("%d\n",ans);
68     return 0;
69 }