树状数组模板（区间修改+单点查询）

Posted 2022-10-03 msmw

很巧妙的用了差分建树，解决区间修改的问题

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 typedef long long ll;
 4 const int maxn=5e5+5;
 5 
 6 int n,m;
 7 int a[maxn];
 8 ll tree[maxn];
 9 
10 int lowbit(int x)
11     return x&(-x);
12 
13 
14 void add(int idx,int v)
15     for(int i=idx;i<=n;i+=lowbit(i))
16         tree[i]+=v;
17  
18 
19 ll sum(int x)
20     ll ans=0;
21     while(x!=0)
22         ans+=tree[x];
23         x-=lowbit(x);
24     
25     return ans;
26     
27 
28 int main()
29     std::ios::sync_with_stdio(false);
30     cin>>n>>m;
31     for(int i=1;i<=n;i++) cin>>a[i],add(i,a[i]-a[i-1]);
32     for(int i=1;i<=m;i++)
33     //cout <<i<<"i=="<<endl;
34         int op,x,y,z;cin>>op;
35         if(op==1) 
36             cin>>x>>y>>z;add(x,z);add(y+1,-z);
37         else 
38             cin>>x;cout <<sum(x)<<"\n";
39     
40     
41     return 0;
42