题解 | 活动安排

#include<bits/stdc++.h>
using namespace std;

int main() {
    int n; 
    cin >> n;
    vector<pair<int, int>> v(n + 1);
    vector<int> g(n + 1);
    g[0] = 0;
    for (int i = 1; i <= n ; i++) cin >> v[i].first >> v[i].second;
    sort(v.begin() + 1, v.end(), [&](pair<int, int> a, pair<int, int> b) {
        return a.second < b.second;
    });
    int ans = 0, pre = 0;
    for (int i = 1; i <= n; i++) if (v[i].first >= pre) ans++, pre = v[i].second;
    cout << ans << endl;
}