题解 | 植树节

#include <bits/stdc++.h>
using namespace std;
long long arr[1000086];
long long sum[1000086];
int main()
{
    int n;
    cin >> n;
    int max = 0;
    while (n--)
    {
        int l, r;
        cin >> l >> r;
        if (r > max)
            max = r;
        arr[l]++;
        arr[r + 1]--;
    }
    sum[0] = arr[0];
    int ans = 0;
    for (int i = 0; i <= max; i++)
    {
        if (i >= 1)
            sum[i] = sum[i - 1] + arr[i];
        if (sum[i] > ans)
            ans = sum[i];
    }
    cout << ans;
    return 0;
}