code:

#include <bits/stdc++.h>
using namespace std;
const int INF = INT_MAX;
const int maxn = 1e5 + 5;
priority_queue<int, vector<int>, greater<int>> a[maxn];
int c[maxn];
multiset<int> s;
int main(){
	int n, m;
	scanf("%d%d", &n, &m);
	for(int i = 1; i <= n; i++){
		scanf("%d", c + i);
	}
	c[n + 1] = INF;
	while(a[n + 1].size()){
		a[n + 1].pop();
	}
	for(int i = 1, s, e; i <= m; i++){
		scanf("%d%d", &s, &e);
		a[s].push(e + 1);
	}
	int ans = 0;
	for(int i = 1; i <= n + 1; i++){
		while(s.size() && *s.begin() == i) s.erase(s.begin()), ans++;
		if(i == n + 1) break;
		if(s.size() > c[i]){
			multiset<int> :: iterator it = s.end();
			it--;
			while(s.size() > c[i]) {
				multiset<int> :: iterator temp = it;
				s.erase(temp);
				it--;
			}
		}
		while(true){
			if(!a[i].size()) break;
			int cur = a[i].top();
			a[i].pop();	
			if(s.size() < c[i]){
				s.insert(cur);
				continue;
			}
			multiset<int> :: iterator it = s.end();
			it--;
			if(*it > cur){
				s.erase(it);
				s.insert(cur);
			} 
			else{
				break;
			}
		}
	}
	printf("%d\n", ans);
	return 0;
} 

在我们校内OJ上用C++11(NOI)才能过，luoguRE，求调。