题解

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

int n,a[3005],b[3005],dp[3005][3005];

int main(){
    int ans = 0;
    cin >> n;
    for(int i = 1;i <= n;i ++) cin >> a[i];
    for(int i = 1;i <= n;i ++) cin >> b[i];
    for(int i = 1;i <= n;i ++){
        int amax = 1;
        for(int j = 1;j <= n;j ++){
            dp[i][j] = dp[i - 1][j];
            if (a[i] == b[j]) dp[i][j] = max(dp[i][j],amax);
            else if (b[j] < a[i]) amax = max(amax,dp[i - 1][j] + 1);
        }
    }
    for(int j = 1;j <= n;j ++){
        ans = max(ans,dp[n][j]);
    }
    cout << ans << endl;
    return 0;
}