POJ 3468 A Simple Problem with Integers

#include <iostream>
#include <cstdio>

using namespace std;

#define maxn 100005
#define lson rt<<1
#define rson rt<<1|1

struct SegmentTree//建立一个结构体存储左右端点与区间内的值
{
    int l,r;
    long long sum,e;
    int Mid()
    {
        return (l+r)>>1;
    }
    int len()
    {
        return r-l+1;
    }
} a[maxn<<2];

void BuildSegTree(int rt,int l,int r)
{
    a[rt].l=l;
    a[rt].r=r;
    a[rt].e=0;
    if(l==r)
    {
        scanf("%lld",&a[rt].sum);
        return ;
    }

    BuildSegTree(lson,l,a[rt].Mid());
    BuildSegTree(rson,a[rt].Mid()+1,r);

    a[rt].sum=a[lson].sum+a[rson].sum;

}
void PushDown(int rt)
{
    a[lson].sum+=a[rt].e*a[lson].len();
    a[lson].e+=a[rt].e;
    a[rson].sum+=a[rt].e*a[rson].len();
    a[rson].e+=a[rt].e;

    a[rt].e=0;
}
void Update(int rt,int l,int r,int e)
{
    a[rt].sum+=(r-l+1)*e;
    if(a[rt].l==l&&a[rt].r==r)
    {
        a[rt].e+=e;
        return ;
    }

    PushDown(rt);

    if(r<=a[rt].Mid())
        Update(lson,l,r,e);
    else if(l>a[rt].Mid())
        Update(rson,l,r,e);
    else
    {
        Update(lson,l,a[rt].Mid(),e);
        Update(rson,a[rt].Mid()+1,r,e);
    }
}

long long Query(int rt,int l,int r)
{
    if(a[rt].l==l&&a[rt].r==r)
    {
        return a[rt].sum;
    }

    PushDown(rt);

    if(r<=a[rt].Mid())
        return Query(lson,l,r);
    else if(l>a[rt].Mid())
        return Query(rson,l,r);
    else
    {
        long long lsum=Query(lson,l,a[rt].Mid());
        long long rsum=Query(rson,a[rt].Mid()+1,r);
        return lsum+rsum;
    }
}

int main()
{
    int n,q;
    while(~scanf("%d%d",&n,&q))
    {
        BuildSegTree(1,1,n);
        while(q--)
        {
            char s[10];
            int l,r,e;
            scanf("%s",s);
            if(s[0]=='Q')
            {
                scanf("%d%d",&l,&r);
                printf("%lld\n",Query(1,l,r));
            }
            else
            {
                scanf("%d%d%d",&l,&r,&e);
                Update(1,l,r,e);
            }

        }
    }

    return 0;
}