hdu1754 I Hate It 线段树RMQ

题目链接:

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

题意:

题解:

线段树RMQ，单点更新，区间查询最大值

代码:

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define MS(a) memset(a,0,sizeof(a))
#define MP make_pair
#define PB push_back
const int INF = 0x3f3f3f3f;
const ll INFLL = 0x3f3f3f3f3f3f3f3fLL;
inline ll read(){
    ll x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}
//////////////////////////////////////////////////////////////////////////
const int maxn = 2e5+10;

int mx[maxn<<2];

void pushup(int rt){
    mx[rt] = max(mx[rt<<1],mx[rt<<1|1]);
}

void build(int l,int r,int rt){
    if(l == r){
        scanf("%d",&mx[rt]);
        return ;
    }   
    int mid = (l+r)/2;
    build(l,mid,rt<<1);
    build(mid+1,r,rt<<1|1);
    pushup(rt);
}

void update(int l,int r,int rt,int p,int va){
    if(l == r){
        mx[rt] = va;
        return ;
    }
    int mid = (l+r)/2;
    if(p<=mid) update(l,mid,rt<<1,p,va);
    else update(mid+1,r,rt<<1|1,p,va);
    pushup(rt);
}

int query(int l,int r,int rt,int L,int R){
    if(L<=l && r<=R){
        return mx[rt];
    }

    int mid = (l+r)/2;
    if(L>mid)
        return query(mid+1,r,rt<<1|1,L,R);
    if(R<=mid)
        return query(l,mid,rt<<1,L,R);
    return max(query(l,mid,rt<<1,L,R),query(mid+1,r,rt<<1|1,L,R));
}

int main(){
    int n,m;
    while(scanf("%d%d",&n,&m) != EOF){
        build(1,n,1);
        for(int i=0; i<m; i++){
            char op; int a,b;
            cin >> op >> a >> b;
            if(op == 'Q')
                cout << query(1,n,1,a,b) << endl;
            else
                update(1,n,1,a,b);  
        }
    }

    return 0;
}