POJ-3468

成段更新的线段树，应该也算比较基础的写法

#include<cstdio>
#include<algorithm>
#include<cstring>

using namespace std;

namespace
{
	typedef long long ll;
	const int MAX_N = (1 << 18) - 1;
	int n, N, Q, a, b, c;
	ll da[MAX_N], db[MAX_N];

	void add(int k, int l, int r)
	{
		if (a <= l && r <= b)
			da[k] += c;
		else if (!(b <= l || a >= r))
		{
			db[k] += (min(r, b) - max(l, a)) * c;
			add(k * 2 + 1, l, (l + r) / 2);
			add(k * 2 + 2, (l + r) / 2, r);
		}
	}

	ll sum(int k, int l, int r)
	{
		if (b <= l || a >= r)
			return 0;
		else if (a <= l && r <= b)
			return (r - l) * da[k] + db[k];
		else
		{
			ll res = (min(r, b) - max(l, a)) * da[k];
			res += sum(k * 2 + 1, l, (l + r) / 2);
			res += sum(k * 2 + 2, (l + r) / 2, r);
			return res;
		}
	}

	ll init(int k)
	{
		if (k >= n - 1)
			return db[k];
		else
			return db[k] = init(2 * k + 1) + init(2 * k + 2);
	}

	void input()
	{
		memset(da, 0, sizeof(da));
		memset(db, 0, sizeof(db));
		scanf("%d %d", &N, &Q);
		n = 1;
		while (n < N)
			n <<= 1;
		for (int i = 0; i < N; i++)
			scanf("%lld", &db[i + n - 1]);
		init(0);
		char s[2];
		while (Q--)
		{
			scanf("%s", s);
			if (s[0] == 'Q')
			{
				scanf("%d %d", &a, &b);
				a--;
				printf("%lld\n", sum(0, 0, n));
			}
			else
			{
				scanf("%d %d %d", &a, &b, &c);
				a--;
				add(0, 0, n);
			}
		}
	}

}

int main()
{
	input();
	return 0;
}