(简单) POJ 3468 A Simple Problem with Integers , 线段树+区间更新。

Description

　　You have N integers, A1, A2, ... , AN. You need to deal with two kinds of operations. One type of operation is to add some given number to each number in a given interval. The other is to ask for the sum of numbers in a given interval.

　　题意很好理解，就是标准的线段树区间更新问题，可以说是模板。

　　不过因为写的不熟练，被坑了两个WA，错的地方在代码里标出来了。。。

代码如下：

#include<iostream>
#include<cstdio>

#define lson L,M,po*2
#define rson M+1,R,po*2+1

using namespace std;

long long BIT[100005*4];
long long COL[100005*4];

void pushUP(int po)
{
BIT[po]=BIT[po*2]+BIT[po*2+1];
}

void pushDown(int po,int len)
{
if(COL[po])
{
BIT[po*2]+=(long long)COL[po]*(len-(len/2));
BIT[po*2+1]+=(long long)COL[po]*(len/2);

COL[po*2]+=COL[po];                 //注意是+=，不是= ！！！
COL[po*2+1]+=COL[po];
COL[po]=0;
}
}

void build_tree(int L,int R,int po)
{
if(L==R)
{
COL[po]=0;
cin>>BIT[po];
return;
}

int M=(L+R)/2;

build_tree(lson);
build_tree(rson);

pushUP(po);
}

long long query(int ql,int qr,int L,int R,int po)
{
if(ql<=L&&qr>=R)
return BIT[po];

pushDown(po,(R-L+1));

int M=(L+R)/2;

if(qr<=M)
return query(ql,qr,lson);
if(ql>M)
return query(ql,qr,rson);

return query(ql,qr,rson)+query(ql,qr,lson);
}

void update(int ul,int ur,int add,int L,int R,int po)
{
if(ul<=L&&ur>=R)
{
BIT[po]+=(long long)add*(R-L+1);
COL[po]+=(long long)add;

return;
}

pushDown(po,R-L+1);

int M=(L+R)/2;

if(ul<=M)
update(ul,ur,add,lson);
if(ur>M)
update(ul,ur,add,rson);

pushUP(po);
}

int main()
{
int N,Q;
char C;
int a,b,c;

while(~scanf("%d %d",&N,&Q))
{
build_tree(1,N,1);

for(int i=0;i<Q;++i)
{
cin>>C;

if(C=='Q')
{
scanf("%d %d",&a,&b);

cout<<query(a,b,1,N,1)<<endl;
}
else
{
scanf("%d %d %d",&a,&b,&c);
update(a,b,c,1,N,1);
}
}
}

return 0;
}

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