POJ 3468 A simple problem with Integers (线段树区间更新，区间查询) 2/5

题目链接：http://poj.org/problem?id=3468

首先，感谢雨巨的线段树入门视频，可算让我整明白线段树的原理，还学到了一些编码的技巧。orz，再次感谢雨巨。

这道题目就是裸的线段树，区间更新，区间查询

代码：

#include<stdio.h>

#define LL long long
struct SeTreeNode
{
    int left,right;
    LL int lazy;
    LL int len;
    LL int sum;
};
SeTreeNode tree[400000];
LL int a[100010];
void build(int id,int l,int r);
void update(int id,int l,int r,LL int val);
void PushDown(int id);

LL query(int id,int l,int r);
int main()
{
    int  T,n,a1,a2,q;
    LL a3;
    char s[12];

    scanf("%d%d",&n,&q);
    for(int i=1 ; i<=n ; i++)
    {
        scanf("%lld",&a[i]);
    }
    build(1,1,n);

    while(q--)
    {
        scanf(" %s",s);

        scanf("%d%d",&a1,&a2);
        if(s[0]=='Q')
        {
            LL int ans=query(1,a1,a2);
            printf("%lld\n",ans);
        }
        if(s[0]=='C')
        {
            scanf("%lld",&a3);
            update(1,a1,a2,a3);

        }
    }

    return 0;
}

void build(int id,int l,int r)
{
    tree[id].left=l,tree[id].right=r;
    tree[id].len=tree[id].right-tree[id].left+1;
    tree[id].lazy=0;
    if(tree[id].left==tree[id].right)
    {
        tree[id].sum=a[l];
        //tree[id].lazy=0;
        //tree[id].len=tree[id].right-tree[id].left+1;
        return ;
    }
    int mid=(l+r)/2;
    build(id*2,l,mid);
    build(id*2+1,mid+1,r);
    tree[id].sum=tree[id*2].sum+tree[id*2+1].sum;
}
LL int query(int id,int l,int r)
{
    if(tree[id].left>=l&&tree[id].right<=r)
        return tree[id].sum;

    if(tree[id].left>r||tree[id].right<l)
        return  0;

    if(tree[id].lazy)
        PushDown(id);

    return query(id*2,l,r)+query(id*2+1,l,r);

}
void update(int id,int l,int r,LL int val)
{
    if(tree[id].left>=l&&tree[id].right<=r)
    {
        tree[id].sum+=val*tree[id].len;
        tree[id].lazy+=val;
        return ;
    }
    if(tree[id].left>r||tree[id].right<l)
        return ;
    if(tree[id].lazy)
        PushDown(id);

    update(id*2+1,l,r,val);

    update(id*2,l,r,val);

    tree[id].sum=tree[id*2].sum+tree[id*2+1].sum;

}
void PushDown(int id)
{
    if(tree[id].lazy)
    {
        tree[id*2].lazy+=tree[id].lazy;
        tree[id*2+1].lazy+=tree[id].lazy;
        tree[id*2].sum+=tree[id].lazy*tree[id*2].len;
        tree[id*2+1].sum+=tree[id].lazy*tree[id*2+1].len;
        tree[id].lazy=0;
    }
}