P11853 [CSP-J2022 山东] 植树节

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int maxn = 1e6+10;
int a[maxn],b[maxn],ans = 0,mr = 0;
signed main(){
	int n; cin >> n;
	for(int i = 1;i <= n;i++){
		int l,r; cin >> l >> r;
        l++,r++;//避免为0
		mr = max(mr,r);//更新最右区间 
		a[l]++,a[r+1]--;//先差分 
	}
	b[0] = a[0];//零也被浇了 
	for(int i = 1;i <= mr;i++) {
		b[i] += b[i-1] + a[i];//前缀和 
		ans = max(ans,b[i]);//取最大值 
	}
	cout << ans;
	return 0;
}