poj3264线段数求最大最小值

链接：https://vjudge.net/contest/66989#problem/G

完完全全的水题，还是被坑了，一个return忘了写，de了半天bug！！

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
#define ll long long
#define ls l,m,rt<<1
#define rs m+1,r,rt<<1|1
const int maxn=50010;
const ll inf=1e15;
ll value1[maxn<<2],value2[maxn<<2];
void pushup(int rt)
{
    value1[rt]=max(value1[rt<<1],value1[rt<<1|1]);
    value2[rt]=min(value2[rt<<1],value2[rt<<1|1]);
}
void btree(int l,int r,int rt)
{
    if(l==r)
    {
        scanf("%lld",&value1[rt]);
        value2[rt]=value1[rt];
        return ;
    }
    int m=(l+r)>>1;
    btree(ls);
    btree(rs);
    pushup(rt);
}
ll query1(int L,int R,int l,int r,int rt)
{
    if(L<=l&&r<=R)return value1[rt];
    int m=(l+r)>>1;
    ll ans=0;
    if(L<=m)ans=max(ans,query1(L,R,ls));
    if(R>m)ans=max(ans,query1(L,R,rs));
    return ans;
}
ll query2(int L,int R,int l,int r,int rt)
{
    if(L<=l&&r<=R)return value2[rt];
    int m=(l+r)>>1;
    ll ans=inf;
    if(L<=m)ans=min(ans,query2(L,R,ls));
    if(R>m)ans=min(ans,query2(L,R,rs));
    return ans;
}
int main()
{
    int n,m;
    while(~scanf("%d%d",&n,&m)){
        btree(1,n,1);
        while(m--){
            int l,r;
            scanf("%d%d",&l,&r);
            printf("%lld\n",query1(l,r,1,n,1)-query2(l,r,1,n,1));
        }
    }
}