树状数组区间更新板子

存一个树状数组区间更新的板子

ll c1[maxn];//c1维护差分数组的前缀和
ll c2[maxn], a[maxn];//c2维护c1 * (pos - 1)的前缀和
//a[i]的前缀和[1, p]可以由c1[1,2,...,p] * p - c2[1,2,...,p]表示
int n;
inline int lowbit(int x)
{
    return x & (-x);
}

void add(int p, int val)
{
    for (int i = p; i <= n; i += lowbit(i))
    {
        c1[i] += val;
        c2[i] += 1ll * val * (p - 1);
    }
}

inline void update(int l, int r, int w)
{
    add(l, w);
    add(r + 1, -w);
}

ll getSum(int p)
{
    ll ans = 0;
    for (int i = p; i > 0; i -= lowbit(i))
        ans += 1ll * p * c1[i] - c2[i];
    return ans;
}