https://blog.csdn.net/qq_34990731/article/details/82889654

https://www.luogu.org/problemnew/show/P3368

#include<iostream>
#include<cstdio>
using namespace std;
int b[500100],n,c[500100];
int lowbit(int i)//樹狀陣列嘗龜操作 
{
   return i&(-i);
}
void change(int i,int num)
{
   while(i<=n)
   {
   	b[i]+=num;//b儲存的是修改的值
   	i+=lowbit(i);
   }
   return ;
}
int sum(int i)
{
   int ans=0;
   while(i>0)
   {
   	ans+=b[i];
   	i-=lowbit(i);
   }
   return ans;
}
int main()
{
   int m;
   scanf("%d %d",&n,&m);
   for(int i=1;i<=n;i++)
   {
   	scanf("%d",&c[i]);//輸入資料 
   }
   for(int i=1;i<=m;i++)
   {
   	int d,x,y,k;
   	scanf("%d",&d);
   	if(d==1)
   	{
   		scanf("%d %d %d",&x,&y,&k);//修改區間 
   		change(x,k);
   		change(y+1,-k);
   	}
   	else 
   	{
   		scanf("%d",&x);
   		int ans;
   		ans=sum(x);//單點查詢 
   		printf("%d \n",ans+c[x]);
   	}
   }
   return 0;
}