bzoj 1588营业额统计(HNOI 2002)

http://www.lydsy.com/JudgeOnline/problem.php?id=1588

splay  bottom-up的数组实现。

题意就是给你一组数，求每个数与在其前面且与其最相近的数的差值的绝对值。

考虑splay二叉搜索树的特性，每新插入一个节点，比它小且最靠近它的数在是左子树中的最大值，另一半同理。

代码借鉴自：http://blog.csdn.net/ACM_cxlove?viewmode=contents

 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 using namespace std;
 const int maxn = 1e5 + ;
 const int inf = 0x3f3f3f3f;
 int pre[maxn], key[maxn], ch[maxn][], root, size;
 int n;

 void new_node(int &r, int father, int k){
     r = ++size;
     pre[r] = father;
     key[r]= k;
     ch[r][] = ch[r][] = ;
 }

 void rotate(int x, bool d){// d = 1, right rotate
     int y = pre[x];
     ch[y][!d] = ch[x][d];
     pre[ch[x][d]] = y;
     if(pre[y]) ch[pre[y]][ch[pre[y]][] == y] = x;
     //if y is not the root, link x with its grandparent
     pre[x] = pre[y];
     ch[x][d] = y;
     pre[y] = x;
 }

 void splay(int u, int dest){
     //root u to root dest
     while(pre[u] != dest){
         if(pre[pre[u]] == dest) rotate(u, ch[pre[u]][] == u);
         else{
             int y = pre[u];
             int d = ch[pre[y]][] == y;
             if(ch[y][d] == u){//zig-zag
                 rotate(u, !d);
                 rotate(u, d);
             }else{
                 rotate(y, d);//zig-zig
                 rotate(u, d);
             }
         }
     }
     if(!dest) root = u;
 }

 int insert(int k){
     int u = root;
     while(ch[u][key[u] < k]){
         if(key[u] == k) return splay(u, ), ;
         u = ch[u][key[u] < k];
     }
     if(key[u] == k) return splay(u, ), ;
     new_node(ch[u][key[u] < k], u, k);
     splay(ch[u][key[u] < k], );
     return ;
 }

 int get_pre(int x){
     int tem = ch[x][];
     if(!tem) return inf;
     while(ch[tem][]) tem = ch[tem][];
     return key[x] - key[tem];
 }

 int get_next(int x){
     int tem = ch[x][];
     if(tem == ) return inf;
     while(ch[tem][]) tem = ch[tem][];
     return key[tem] - key[x];
 }

 int main(){
     //freopen("in.txt", "r", stdin);
     while(~scanf("%d", &n)){
         root = size = ;
         int ans = ;
         for(int i = ; i <= n; i++){
             int num;
             if(scanf("%d", &num) == EOF) num = ;
             if(i == ){
                 ans += num;
                 new_node(root, , num);
                 continue;
             }
             if(!insert(num)) continue;
             int a = get_next(root);
             int b = get_pre(root);
             ans += min(a, b);
         }
         printf("%d\n", ans);
     }
     return ;
 }