自用模板，树状数组

include <string.h>

include <stdio.h>

include

include

using namespace std;
int n,m,a[11000],c[11000];
//差分建树，区间更新
int lowbit(int x)
{
return x&-x;
}
void updata(int i,int k)//单点更新
{
while(i<=n)
{
c[i]+=k;
i+=lowbit(i);
}
}
int getsum(int i)//单点查询
{
int sum=0;
while(i>0)
{
sum+=c[i];
i-=lowbit(i);
}
return sum;
}
//区间查询

int main()
{
cin>>n;
for (i=1;i<=n;i++)
{
cin>>a[i];
updata(i,a[i]-a[i-1]);//输入初值的时候，也相当于更新了值
}
//区间更新(还是单点...)
//[x,y]区间内加上k
updata(x,k);
updata(y+1,-k);

return 0;

}

---

include <string.h>

include <stdio.h>

include

using namespace std;
int n,m,a[11000],sum1[11000],sum2[11000];
int lowbit(int x)
{
return x&-x;
}
void updata(int i,int k)
{
int x=i;
while(i<=n)
{
sum1[i]+=k;
sum2[i]+=k(x-1);
i+=lowbit(i);
}
}
int getsum(int i)//求前缀和
{
int res=0,x=i;
while (i>0)
{
res+=xsum1[i]-sum2[i];
i-=lowbit(i);
}
return res;
}
int main()
{
int i,j;
cin>>n;
for (i=1;i<=n;i++)
{
cin>>a[i];
updata(i,a[i]-a[i-1]);//差分
}
//[x,y]区间内加上k
updata(x,k);
updata(y+1,-k);

int sum=getsum(y)-getsum(x-1);//求区间和 

return 0;

}