精妙的线段树区间修改部分注释

#include<algorithm>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<iostream>
#include<vector>
#include<queue>
#include<stack>
#include<iomanip>
#include<string>
#include<climits>
#include<cmath>
#define MAX 110000
#define LL long long
using namespace std;
LL n,m;
LL ans;
struct Tree
{
	LL l,r;
	LL sum,add;
};
Tree tree[MAX*3];

void pushup(LL x)//更新
{
	LL tmp=2*x;
	tree[x].sum=tree[tmp].sum+tree[tmp+1].sum;
}


void pushdown(LL x)//传递标记并更新
{
	LL tmp=2*x;
	tree[tmp].add+=tree[x].add;
	tree[tmp+1].add+=tree[x].add;
	tree[tmp].sum+=tree[x].add*(tree[tmp].r-tree[tmp].l+1);
	tree[tmp+1].sum+=tree[x].add*(tree[tmp+1].r-tree[tmp+1].l+1);
	tree[x].add=0;
}

void build(int l,int r,int x)
{
	tree[x].l=l;
	tree[x].r=r;
	tree[x].add=0;
	if(l==r)
	{
		scanf("%lld",&tree[x].sum);
		return ;
	}
	int tmp=x<<1;
	int mid=(l+r)>>1;
	build(l,mid,tmp);
	build(mid+1,r,tmp+1);
	pushup(x);	 //如果在建树的过程中给sum赋值，记得后面要pushup
}


void update(LL l,LL r,LL c,LL x)
{
	if(r<tree[x].l||l>tree[x].r)
		return ;
	if(l<=tree[x].l&&r>=tree[x].r)
	{
		tree[x].add+=c;
		tree[x].sum+=c*(tree[x].r-tree[x].l+1);
		return ;
	}
	if(tree[x].add)
		pushdown(x);    //需要分段 传递标记
	LL tmp=x<<1;
	update(l,r,c,tmp);	//  !!!
	update(l,r,c,tmp+1);
	pushup(x);              //此时x结点sum未更新 更新sum
}


void query(LL l,LL r,LL x)
{
	if(r<tree[x].l||l>tree[x].r)		 //要更新的区间不在该区间上 l r tl tr或tl tr l r
		return ;
	if(l<=tree[x].l&&r>=tree[x].r)	  //要更新区间包括了该区间 l tl tr r
	{
		ans+=tree[x].sum;
		return ;
	}
	if(tree[x].add)
		pushdown(x);
	LL tmp=x<<1;
	LL mid=(tree[x].l+tree[x].r)>>1;
	if(r<=mid)
		query(l,r,tmp);            //tl l r mid tr(l,r)
	else if(l>mid)
		query(l,r,tmp+1);          //tl mid l r tr(l,r)
	else
	{                                  //总tl l mid r tr (l,r)
		query(l,mid,tmp);          //左(l,mid)
		query(mid+1,r,tmp+1);      //右(mid+1,r)
	}
//	pushup(x);
}


int main()
{
//	freopen("cin.txt","r",stdin);
//	freopen("cout.txt","w",stdout);
	while(~scanf("%lld %lld",&n,&m))
	{
		build(1,n,1);
		char str[5];
		while(m--)
		{
			scanf("%s",str);
			if(str[0]==‘Q‘)
			{
				LL l,r;
				scanf("%lld %lld",&l,&r);
				ans=0;
				query(l,r,1);
				printf("%lld\n",ans);
			}
			else
			{
				LL l,r,c;
				scanf("%lld %lld %lld",&l,&r,&c);
				update(l,r,c,1);
			}
		}
	}
	return 0;
}