Uva 11362 - Phone List

Time Limit is big which is unnecessary. I think, 3 sec Time Limit may be a good Time Limit for that Problem :)

#include<bits/stdc++.h>

using namespace std;

typedef vector<string>vs;

bool Ischeck(string x, string y)
{
    int i,len=x.size();
    bool fl=false;
    for(i=0;i<len;i++)
    {
        if(x[i] != y[i])
        {
            return true;
        }
    }

    return false;
}

int main()
{
    int t;
    vs v;
    cin >> t;
    while(t--)
    {
        v.clear();
        int n;
        cin >> n;
        getchar();

        string s;
        int i;

        for(i=0;i<n;i++)
        {
            cin >> s;
            v.push_back(s);
        }

        sort(v.begin(),v.end());
        //for(i=0;i<n;i++)cout << v[i] << " ";
        if(n==1)
        {
            cout << "YES" << endl;
            continue;
        }

        bool f=false;
        for(i=0;i<n-1;i++)
        {
            if(Ischeck(v[i],v[i+1]))
            {
                f=true;
            }
            else
            {
                f=false;
                break;
            }
        }

        if(f)
        {
            cout << "YES" << endl;
        }
        else
        {
            cout << "NO" << endl;
        }
    }

    return 0;
}