BZOJ1588 HNOI2002 营业额统计 [Splay入门题]

 1 /**/
 2 #include<iostream>
 3 #include<cstdio>
 4 #include<cmath>
 5 #include<cstring>
 6 #include<algorithm>
 7 using namespace std;
 8 int INF=100000000;
 9 const int mxn=120000;
10 int v[mxn],ch[mxn][2],fa[mxn],root=0,cnt=0;
11 int t1,t2;
12 int n;
13 void rotate(int x,int &k){
14     int y=fa[x],z=fa[y];
15     int l,r;
16     if(ch[y][0]==x) l=0; else l=1;
17     r=l^1;
18     if(y==k)k=x;
19     else{
20         if(ch[z][0]==y) ch[z][0]=x;
21         else ch[z][1]=x;
22         }
23     fa[x]=z;fa[y]=x;fa[ch[x][r]]=y;
24     ch[y][l]=ch[x][r];
25     ch[x][r]=y;
26 }
27 void splay(int x,int &k){
28     int y,z;
29     while(x!=k){
30         y=fa[x];z=fa[y];
31         if(y!=k){
32             if((ch[y][0]==x)^(ch[z][0]==y))rotate(x,k);
33             else rotate(y,k);
34         }
35         rotate(x,k);
36     }
37     return;
38 }
39 void insert(int &k,int val,int father){
40     if(!k){
41         k=++cnt;
42         v[k]=val;
43         fa[k]=father;
44         splay(k,root);
45         return;
46     }
47     if(val<v[k]) insert(ch[k][0],val,k);
48     else if(val>v[k]) insert(ch[k][1],val,k);
49 }
50 void ask_1(int k,int x){//求前驱 
51     if(!k)return;
52     if(x>=v[k]){
53         t1=v[k];
54         ask_1(ch[k][1],x);
55     }else ask_1(ch[k][0],x);
56     return;
57 }
58 void ask_2(int k,int x){//求前驱 
59     if(!k)return;
60     if(x<=v[k]){
61         t2=v[k];
62         ask_2(ch[k][0],x);
63     }else ask_2(ch[k][1],x);
64     return;
65 }
66 int main(){
67     scanf("%d",&n);
68     int i,j,x;
69     bool first=1;
70     int ans=0;
71     for(i=1;i<=n;i++){
72         scanf("%d",&x);
73         t1=-INF;
74         t2=INF;
75         if(first){
76             first=0;
77             ans+=x;
78         }
79         else {
80             ask_1(root,x);
81             ask_2(root,x);
82             ans+=min(x-t1,t2-x);
83         }
84         insert(root,x,0);
85     }
86     printf("%d\n",ans);
87     return 0;
88 }