242. 一个简单的整数问题树状数组的简单扩展 区间修改 单点查询

Posted 2021-10-30 幽殇默

https://www.acwing.com/problem/content/description/248/

#include<bits/stdc++.h>
using namespace std;
const int N=1e5+10;
typedef long long int LL;
LL a[N],tr[N],n,m;
int lowbit(int x){return x&(-x);}
void add(int x,int c)
{
    for(int i=x;i<=n;i+=lowbit(i)) tr[i]+=c;
}
LL sum(int x)
{
    LL res=0;
    for(int i=x;i;i-=lowbit(i)) res+=tr[i];
    return res;
}
int main(void)
{
    cin>>n>>m;
    for(int i=1;i<=n;i++) cin>>a[i];
    for(int i=1;i<=n;i++) add(i,a[i]-a[i-1]);
    while(m--)
    {
        string op; cin>>op;
        if(op=="C")
        {
            int l,r,c; cin>>l>>r>>c;
            add(l,c),add(r+1,-c);
        }
        else
        {
            int x; cin>>x;
            cout<<sum(x)<<endl;
        }
    }
    return 0;
}