树状数组【区间修改+单点查询】

https://www.luogu.com.cn/problem/P3368

#include<bits/stdc++.h>
using namespace std;
#define endl '\n'
#define lowbit(x)  x&(-x)
using ll = long long;
using pii = pair<int, int>;
const double PI = acos(-1);
const int N = 5e5 + 10;
const int mod = 1e9 + 7;
ll c[N],a[N];
int n,m;
void updata(int x,int k){
	for(int i=x;i<=n;i+=lowbit(i))
		c[i]+=k;
}
ll query(int x){
	ll sum=0;
	for(int i=x;i;i-=lowbit((i))){
		sum+=c[i];
	}
	return sum;
}
void solve() {
	cin>>n>>m;
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}
	for(int i=1;i<=n;i++)
	{
		int x=a[i]-a[i-1];
		updata(i,x);
	}	
	while(m--){
		int ch;cin>>ch;
		if(ch==1){
			int x,y,k;cin>>x>>y>>k;
			updata(x,k);
			updata(y+1,-k);

		}
		else{
			int x;cin>>x;
			cout<<query(x)<<endl;
		}
	}
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr), cout.tie(nullptr);
	
	int T = 1;
	//cin>>T;
	while (T--) {
		solve();
	}
	
	return 0;
}