解题思路

代码

#include <iostream>
#include <algorithm>

using namespace std;

typedef pair<int,int> PII;
const int N = 5010;
PII a[N];
int f[N];
int n;

int main() {
    cin >> n;
    for (int i = 0; i < n; i++) cin >> a[i].first >> a[i].second;

    sort(a, a + n);
    int res = 0;
    for (int i = 0; i < n; i++) {
        f[i] = 1;
        for (int j = 0; j < i; j++) {
            if (a[j].second < a[i].second) f[i] = max(f[i], f[j] + 1);
        }
        res = max(res, f[i]);
    }
    cout << res << endl;

    return 0;
}