区间和

/*
输入样例：
3 3
1 2
3 6
7 5
1 3
4 6
7 8
输出样例：
8
0
5
*/
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
const int N = 300010;
typedef pair<int, int> PII;
int n, m;
int a[N], s[N];
vector<int> alls;
vector<PII> add, query;
int find(int x)
{
	int l = 0, r = alls.size() - 1;
	while (l < r)
	{
		int mid = l + r >> 1;
		if (alls[mid] >= x) r = mid;
		else l = mid + 1;
	}
	return r + 1;
}
int main()
{
	cin >> n >> m;
	for (int i = 0; i < n; i++)
	{
		int x, c;
		cin >> x >> c;
		add.push_back({ x, c });
		alls.push_back(x);
	}
	for (int i = 0; i < m; i++)
	{
		int l, r;
		cin >> l >> r;
		query.push_back({ l, r });
		alls.push_back(l);
		alls.push_back(r);
	}
	sort(alls.begin(), alls.end());
	alls.erase(unique(alls.begin(), alls.end()), alls.end());
	for (auto item : add)
	{
		auto x = find(item.first);
		a[x] += item.second;
	}
	for (int i = 1; i <= alls.size(); i++)
	{
		s[i] = s[i - 1] + a[i];
	}
	for (auto item : query)
	{
		int l = find(item.first), r = find(item.second);
		cout << s[r] - s[l - 1] << endl;
	}
	return 0;
}

区间合并

/*
输入样例：
5
1 2
2 4
5 6
7 8
7 9
输出样例：
3
*/
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
const int N = 1e6 + 10;
int n;
typedef pair<int, int> PII;
vector<PII> segs;
void merge(vector<PII> &segs)
{
	vector<PII> res;
	sort(segs.begin(), segs.end());
	int sd = -2e9, ed = -2e9;
	for (auto seg : segs)
		if (ed < seg.first)
		{
			if (sd != -2e9) res.push_back({ sd, ed });
			sd = seg.first, ed = seg.second;
		}
		else ed = max(ed, seg.second);
	if (sd != -2e9) res.push_back({ sd, ed });
	segs = res;
}
int main()
{
	cin >> n;
	for (int i = 0; i < n; i++)
	{
		int l, r;
		cin >> l >> r;
		segs.push_back({ l, r });
	}
	merge(segs);
	cout << segs.size() << endl;
	return 0;
}