[CF915E]Physical Education Lessons（咕咕咕）

#include <cstdio>
#include <algorithm>
#include <cstring>
#include <set>
#include <iostream>

int n, q, ans;

namespace ODT {
	struct node {
		int l, r;
		mutable int v;
		inline bool operator < (const node &rhs) const {
			return l < rhs.l;
		}
	} ;
	std::set<node> s;
	typedef std::set<node>::iterator SIT;
	SIT split(int pos) {
		SIT it = s.lower_bound((node) { pos, 0, 0 });
		if (it != s.end() && it -> l == pos) return it;
		--it; const int l = it -> l, r = it -> r, v = it -> v;
		s.erase(it), s.insert((node) { l, pos - 1, v });
		return s.insert((node) { pos, r, v}).first;
	}
	void assign(int l, int r, int v) {
		SIT R = split(r + 1), L = split(l);
		for (SIT it = L; it != R; ++it)
			ans -= it -> v * (it -> r - it -> l + 1);
		s.erase(L, R), s.insert((node) { l, r, v });
		ans += v * (r - l + 1);
	}
}

int main() {
	std::ios::sync_with_stdio(false), std::cin.tie(0), std::cout.tie(0);
	std::cin >> n >> q; ans = n;
	ODT::s.insert((ODT::node) { 1, n, 1 });
	while (q --> 0) {
		static int l, r, x;
		std::cin >> l >> r >> x; --x;
		ODT::assign(l, r, x);
		std::cout << ans << ‘\n‘;
	}
	return 0;
}