Splay解决区间问题[单点更新，区间最值询问]

/*http://acm.hdu.edu.cn/showproblem.php?pid=1754*/
/*单点更新，区间询问 splay实现*/
/*注意写rotateTo的时候。。*/
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int MAXN = 222222;
class SplayTree{
    #define l(x) (ch[x][0])
    #define r(x) (ch[x][1])
    #define mid(x,y) (x+y)>>1
public:
    int ch[MAXN][2],pre[MAXN],sz[MAXN],mx[MAXN],val[MAXN],a[MAXN];
    int root,tot;
    void init(){
        memset(ch,0,sizeof(int)*MAXN*2);
        memset(pre,0,sizeof(int)*MAXN);
        memset(sz,0,sizeof(int)*MAXN);
        memset(mx,-1,sizeof(int)*MAXN);
        root = tot = 0;
    }
    void read(int n){
        a[1] = a[n+2] = -1;
        for(int i=2;i<=n+1;i++) scanf("%d",&a[i]);
    }
    void push_up(int rt){
        mx[rt] = max(max(mx[l(rt)],mx[r(rt)]),val[rt]);
        sz[rt] = sz[l(rt)]+sz[r(rt)]+1;
    }
    void rotate(int x,int f){
        int y = pre[x];
        ch[y][!f] = ch[x][f];
        if(ch[y][!f]) pre[ch[y][!f]] = y;
        push_up(y);
        if(pre[y]) ch[pre[y]][r(pre[y])==y] = x;
        pre[x] = pre[y];
        ch[x][f] = y;
        pre[y] = x;
    }
    void splay(int x,int goal){
        while(pre[x]!=goal){
            int y = pre[x], z = pre[pre[x]];
            if(z==goal){
                rotate(x,l(y)==x);
            }else{
                int f = (l(z)==y);
                if(ch[y][!f]==x){
                    rotate(y,f); rotate(x,f);
                }else{
                    rotate(x,!f); rotate(x,f);
                }
            }
        }
        push_up(x);
        if(goal==0) root = x;
    }
    void rotateTo(int x,int goal){
        int k = root;
        while(1){
            if(x<(sz[l(k)]+1)) k = l(k);
            else if(x==(sz[l(k)]+1)){
                break;
            }else{
                x -= (sz[l(k)]+1);
                k = r(k);
            }
        }
        splay(k,goal);
    }
    void buildTree(int l,int r,int &rt,int f){
        if(l>r)return;
        int m = mid(l,r);
        rt = ++tot;
        val[rt] = a[m];
        pre[rt] = f;
        buildTree(l,m-1,l(rt),rt);
        buildTree(m+1,r,r(rt),rt);
        push_up(rt);
    }
    int query(int l,int r){
        rotateTo(l-1,0);
        rotateTo(r+1,root);
        return mx[l(r(root))];
    }
    void update(int pos,int c){
        rotateTo(pos,0);
        val[root] = c;
        push_up(root);
    }
    void debug(){
        printf("root:%d l(root):%d r(root):%d\n",root,l(root),r(root));
        dfs(root);
    }
    void dfs(int rt){
        if(!rt)return;
        dfs(l(rt));
        printf("node:%d max:%d size:%d val:%d lson:%d rson:%d pre:%d\n",rt,mx[rt],sz[rt],val[rt],l(rt),r(rt),pre[rt]);
        dfs(r(rt));
    }
};
SplayTree spt;
int main(){
    int n,m;
    while(scanf("%d%d",&n,&m)!=EOF){
        spt.init();
        spt.read(n);
        spt.buildTree(1,n+2,spt.root,0);
        char op[2]; int a,b;
        while(m--){
            scanf("%s%d%d",op,&a,&b);
            //spt.debug(); system("pause");
            if(op[0]=='Q'){
                printf("%d\n",spt.query(a+1,b+1));
            }else{
                spt.update(a+1,b);
            }
        }
    }
    return 0;
}