242. 一个简单的整数问题

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long ll;
const int maxn=1e5+1; 
ll a[maxn],tree[maxn],n,m,l,r,k;
char op[2];
ll lowbit(ll x)
{
    return x&-x;
}
void add(ll x,ll k)
{
    while(x<=n)
    {
        tree[x]+=k;
        x+=lowbit(x);
    }
}
ll getsum(ll x)
{
    ll res=0;
    while(x)
    {
        res+=tree[x];
        x-=lowbit(x);
    }
    return res;
}
int main()
{
    cin>>n>>m;
    for (int i = 1; i <= n; i ++ )
        scanf("%lld",a+i);
    while(m--)
    {
        scanf("%s",op);
        if(strcmp(op,"Q")==0)
        {
            scanf("%lld",&l);
            printf("%lld\n",a[l]+getsum(l));
        }
        else if(strcmp(op,"C")==0)
        {
            scanf("%lld%lld%lld",&l,&r,&k);
            add(l,k);add(r+1,-k);
        }
    }
    return 0;
}

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