SPOJ PHONELST

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

const int OO = 1e9;
const double EPS = 1e-9;

class Trie {
    Trie * c[10];
    bool flag;

    public:
    Trie() {
        memset(c,0,sizeof(c));
        flag = 0;
    }

    ~Trie() {
        for(int i = 0; i < 10; i++) {
            if(c[i]) {
                delete c[i];
            }

        }
    }

    bool add(string &s, int idx = 0, bool cn = 0) {
        if(flag) {
            return false;
        }
        if(idx == s.size()) {
            flag = 1;
            return cn;
        }
        int curr = s[idx]-'0';
        if(c[curr] == 0) {
            c[curr] = new Trie();
            cn = 1;
        }
        return c[curr]->add(s,idx+1, cn);
    }
};

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    int t;
    cin >> t;
    while(t--) {
        int n;
        cin >> n;
        Trie dict;
        bool con = true;
        for(int i = 0; i < n; i++) {
            string s;
            cin >> s;
            if(!dict.add(s)) {
                con = false;
            }
        }
        cout << (con ? "YES\n":"NO\n");
    }
    return 0;
}