[HDU 1754] I Hate It Splay

http://acm.hdu.edu.cn/showproblem.php?pid=1754

题意：略

继续splay。。。。

#include <cstdio>#include <cstring>#include <iostream>using namespace std;/const int maxn = 200005;struct Tree{    int val, maxval;    int pre, chd[2];};int n, m;Tree tr[maxn];int F(int rt){    return tr[tr[rt].pre].chd[1] == rt;}void PushUp(int rt)  //向上更新{    tr[tr[rt].chd[0]].pre = rt;    tr[tr[rt].chd[1]].pre = rt;    tr[rt].maxval = tr[rt].val;    if(tr[rt].maxval < tr[tr[rt].chd[0]].maxval){   //更新最大值        tr[rt].maxval = tr[tr[rt].chd[0]].maxval;    }    if(tr[rt].maxval < tr[tr[rt].chd[1]].maxval){    //更新最大值        tr[rt].maxval = tr[tr[rt].chd[1]].maxval;    }}void Rotate(int rt)      //旋转，将rt转到它父结点的位置{    int chd = F(rt);  //判断自己是哪一个孩子    int pre = tr[rt].pre;    tr[rt].pre = tr[pre].pre;    tr[tr[pre].pre].chd[F(pre)] = rt;    tr[pre].chd[chd] = tr[rt].chd[!chd];    tr[rt].chd[!chd] = pre;    PushUp(pre);    PushUp(rt);}int Splay(int rt, int rw){    while(tr[rw].pre != rt){        int pre = tr[rw].pre;        if(F(rw) != F(pre) || tr[pre].pre == rt){  //单旋转            Rotate(rw);        }        else{     //双旋转            Rotate(pre);            Rotate(rw);        }    }    if(rt)   //防止更新0        PushUp(rt);    return rw;}int BuildTree(int Size){    for(int i = 0; i <= Size; i++){        tr[i].pre = i - 1;        tr[i].chd[0] = 0;        tr[i].chd[1] = i + 1;    }    tr[0].pre = 0;    tr[0].val = tr[0].maxval = 0;    tr[1].pre = 0;    tr[1].val = tr[1].maxval = 0;    tr[Size].chd[1] = 0;    tr[Size].val = tr[Size].maxval = 0;    return 1;}int main(){    int rt;    while(~scanf("%d%d", &n, &m)){        for(int i = 1; i <= n; i++){            scanf("%d", &tr[i+1].val);        }        rt = BuildTree(n + 2);        rt = Splay(0, n + 2);        int x, y;        char str[5];        while(m--){            scanf("%s%d%d", str, &x, &y);            if(str[0] == 'U'){                rt = Splay(0, x + 1);                tr[rt].val = y;                PushUp(rt);            }            else{                if(x > y)                    swap(x, y);                rt = Splay(0, x);                Splay(rt, y + 2);                printf("%d\n", tr[tr[tr[rt].chd[1]].chd[0]].maxval);            }        }    }    return 0;}