HDU 1754——I Hate It——————【线段树单点替换、区间求最大值】

#include<stdio.h>
#include<string.h>
#include<algorithm>
using namespace std;
const int maxn=210000;
int maxv[maxn*4];
#define mid (L+R)/2
#define lson rt*2,L,mid
#define rson rt*2+1,mid+1,R
void PushUP(int x){

    maxv[x]=max(maxv[x*2],maxv[x*2+1]);
}
void build(int rt,int L,int R){

    if(L==R){

        scanf("%d",&maxv[rt]);
    }else{

        build(lson);
        build(rson);
        PushUP(rt);
    }
}
void update(int rt,int L,int R,int x,int v){

    if(L==R){

        maxv[rt]=v;
        return ;
    }
    if(mid>=x)
        update(lson,x,v);
    else
        update(rson,x,v);
    PushUP(rt);
}
int query(int rt,int L,int R,int lp,int rp){

    if(lp<=L&&R<=rp){

        return maxv[rt];
    }
    int ret=0;
    if(lp<=mid){

        ret=max(ret,query(lson,lp,rp));
    }
    if(rp>mid){

        ret=max(ret,query(rson,lp,rp));
    }
    return ret;
}
int main(){

    int n,m;
    char tms[5];
    while(scanf("%d%d",&n,&m)!=EOF){
        
        memset(maxv,0,sizeof(maxv));
        build(1,1,n);
        for(int i=0;i<m;i++){

            int a,b,ans;
            scanf("%s%d%d",tms,&a,&b);
            if(tms[0]==‘Q‘){

                ans=query(1,1,n,a,b);
                printf("%d\n",ans);
            }else{

                update(1,1,n,a,b);
            }
        }

    }

    return 0;
}