HDU 4585 Shaolin Splay 寻找前驱后继_splay前驱和后继-优快云博客

本文链接：https://blog.youkuaiyun.com/SolarDomo/article/details/52668342

本文介绍了一道关于Splay树的数据结构题目，通过插入元素并寻找其在排序集合中的前驱与后继来实现。文章提供了完整的C++代码实现，展示了如何利用Splay树进行高效的元素插入和查找操作。

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题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=4585
每次添加一个数在集合中，并寻找这个数在集合排序后的前驱和后继
Splay模板题
每次将节点插入后查找根左子树最右节点和根右子树最左节点

代码：

#include <bits/stdc++.h>
#define sf scanf
#define pf printf
using namespace std;
const int maxn = 100000 + 50,INF = 0x7fffffff;
/** ---- SPLAY ---- **/
int ch[maxn][2],fa[maxn],size[maxn];
int key[maxn],pos[maxn];
int tot,root,sroot;
void Splay_Init(){
    tot = 1;
    root = sroot = 0;
    ch[0][0] = ch[0][1] = 0;
    fa[0] = 0;
    key[0] = INF;
    size[0] = 0;
}
int NewNode(int FA,int k,int p){
    ch[tot][0] = ch[tot][1] = 0;
    fa[tot] = FA;
    size[tot] = 1;
    key[tot] = k,pos[tot] = p;
    return tot++;
}
void PushUp(int rt){size[rt] = 1 + size[ch[rt][0]] + size[ch[rt][1]];}
void rotate(int rt,int kind){
    int prt = fa[rt];
    ch[prt][kind] = ch[rt][!kind];fa[ch[rt][!kind]] = prt;
    ch[fa[prt]][ch[fa[prt]][1] == prt] = rt;fa[rt] = fa[prt];
    ch[rt][!kind] = prt;fa[prt] = rt;
    PushUp(prt);PushUp(rt);
}
void Splay(int rt,int goal){
    while(fa[rt] != goal){
        if(fa[fa[rt]] == goal) rotate(rt,ch[fa[rt]][1] == rt);
        else{
            int prt = fa[rt],kind = (ch[fa[prt]][1] == prt);
            if(ch[prt][kind] == rt) rotate(rt,kind),rotate(rt,kind);
            else rotate(rt,!kind),rotate(rt,kind);
        }
    }
    if(fa[rt] == sroot) root = rt;
}
void Insert(int rt,int k,int p){
    while(ch[rt][k > key[rt]]) rt = ch[rt][k > key[rt]];
    rt = (ch[rt][k > key[rt]] = NewNode(rt,k,p));
    Splay(rt,sroot);
}
int Find(int rt,int k){
    while(ch[rt][k >= key[rt]])
        if(k == key[rt]) return rt;
        else rt = ch[rt][k >= key[rt]];
    return sroot;
}
int Find_Pre(int rt,int k){
    rt = Find(rt,k);
    Splay(rt,sroot);
    if(ch[rt][0] == sroot) return sroot;
    else rt = ch[rt][0];
    while(ch[rt][1]) rt = ch[rt][1];
    return rt;
}
int Find_Next(int rt,int k){
    rt = Find(rt,k);
    Splay(rt,sroot);
    if(ch[rt][1] == sroot) return sroot;
    else rt = ch[rt][1];
    while(ch[rt][0]) rt = ch[rt][0];
    return rt;
}

int main(){
    int n;
    while( ~sf("%d",&n) && n ){
        int x,y,u,d;
        Splay_Init();
        Insert(root,(int)1e9,1);
        while(n--){
            sf("%d%d",&x,&y);
            Insert(root,y,x);
            u = Find_Next(root,y);
            d = Find_Pre(root,y);
            if(u == sroot) pf("%d %d\n",x,pos[d]);
            else if(d == sroot) pf("%d %d\n",x,pos[u]);
            else {

                if(key[u] - y < y - key[d]) pf("%d %d\n",x,pos[u]);
                else pf("%d %d\n",x,pos[d]);
            }

        }
    }
    return 0;
}