HDU 1754

选最大值。线段树。

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <climits>
#include <string.h>
#include <queue>
#include <cmath>
#include <map>
#include <vector>
#define LL  __int64
using namespace std;

const int N=200010;
const int root=1;
struct Node{
	int val,left,right;
}tree[N*4+100];
int n,m;
int score[N],pos[N];

void build(int rt,int l,int r){
	if(l==r){
		tree[rt].val=score[l];
		tree[rt].left=l;
		tree[rt].right=r;
		pos[l]=rt;
		return;
	}
	tree[rt].left=l;
	tree[rt].right=r;
	build(rt*2,l,(r+l)/2);
	build(rt*2+1,(r+l)/2+1,r);
	tree[rt].val=max(tree[rt*2].val,tree[rt*2+1].val);
}

int query(int now,int l,int r){
	int L=tree[now].left ,R=tree[now].right;
	if(l<=L&&r>=R){
		return tree[now].val;
	}
	int m=(L+R)/2;
	if(l>=m+1){
		return query(now*2+1,l,r);
	}
	else if(r<=m) return query(now*2,l,r);
	else{
		return max(query(now*2,l,r),query(now*2+1,l,r));
	}
}

void update(int now,int s){
	tree[now].val=s;
	now/=2;
	while(now>0){
		tree[now].val=max(tree[now*2].val,tree[now*2+1].val);
		now/=2;
	}
}

int main(){
	int p,q; char act;
	while(scanf("%d%d",&n,&m)!=EOF){
		for(int i=1;i<=n;i++)
		scanf("%d",&score[i]);
		getchar();
		build(root,1,n);
		for(int i=1;i<=m;i++){
			scanf("%c%d%d",&act,&p,&q);
			getchar();
//			cout<<act<<p<<q<<endl;
			if(act==‘Q‘){
				printf("%d\n",query(root,p,q));
			}
			else{
				p=pos[p];
				update(p,q);
			}
		}
	}
	return 0;
}