hdu 1754 I Hate It（单点更新，区段查最值）

const int maxn = 200010;
int maxs[maxn<<2];

int N,M;


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

void build(int l,int r,int rt){
    if(l==r){
        scanf("%d",&maxs[rt]);
        return;
    }
    int m = (l + r) >> 1;
    build(lson);
    build(rson);
    PushUp(rt);
}

void update(int p,int add,int l,int r,int rt){
    if(l==r){
        maxs[rt] = add;
        return;
    }
    int m = (l + r) >> 1;
    if(p <= m) update(p,add,lson);
    else update(p,add,rson);
    PushUp(rt);
}

int query(int L,int R,int l,int r,int rt){
    if(L<=l && r<=R){
        return maxs[rt];
    }
    int m = (l + r) >> 1;
    int ret = 0;
    if(L <= m) ret = max( ret, query(L,R,lson) );
    if(R > m) ret = max( ret, query(L,R,rson) );
    return ret;
}





int main(){

    while(scanf("%d%d",&N,&M)!=EOF){

        build(1,N,1);

        for(int i=1;i<=M;++i){
            char c;
            int a,b;
            getchar();
            scanf("%c%d%d",&c,&a,&b);
            if(c == ‘Q‘) printf("%d\n",query(a,b,1,N,1));
            else if(c == ‘U‘) update(a,b,1,N,1);
        }

    }

}