Codeforces 861D - Polycarp's phone book

#include<bits/stdc++.h>
using namespace std;
#define f first
#define s second
#define pb push_back
#define mp make_pair
map<string,int> ma;
string ans[70005];
int main(){
    int n;
    string s,nu;
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>s;
        ans[i+1] = "";
        for(int j=0;j<9;j++){
            nu = "";
            for(int k=j;k<9;k++){
                nu += s[k];
                if(ma[nu] && ma[nu]!=i+1) ma[nu]=-1;
                else ma[nu] = i+1;
            }
        }
    }
    for(auto it : ma){
        if(it.s!=-1)
            if(ans[it.s]=="" || ans[it.s].size()>it.f.size() )
                ans[it.s] = it.f;
    }
    for(int i=1;i<=n;i++)
        cout<<ans[i]<<endl;
    return 0;
}