Checking if the list of given codes can be used to decode any possible string uniquely.

uniquely_decoding_possibilty.cpp

// the algorithm is known as Sardinas–Patterson algo.

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

// in-short-use macros

#define ll long long int
#define ld long double
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define mod 1000000007

//container-use 

typedef vector< ll > vl;
typedef vector< vl > vvl;
typedef pair< ll,ll > pll;
typedef vector<pair<ll,ll > > vpl;
#define all(c) (c).begin(),(c).end()
#define tr(c,i) for(typeof((c).begin() i = (c).begin(); i != (c).end(); i++)
#define present(c,x) ((c).find(x) != (c).end())
#define rep(i,a,b) for (int i = a; i <= b; i++)

//main function here

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    #ifndef ONLINE_JUDGE
//     freopen("C:/Users/Saurav Kumar Singh/Desktop/cp/input.txt", "r", stdin);
//     freopen("C:/Users/Saurav Kumar Singh/Desktop/cp/output.txt", "w", stdout);
    #endif
    cout<<"-----Welcome to the unique decoding system-----\n\n";
    string s;
    cout<<"Enter the number of codes: \n";
    int n;
    cin>>n;
    set<string> se;
    queue<string> q;
    for(int i=0;i<n;i++)
    {
        cin>>s;
        se.insert(s);
        q.push(s);
    }
    bool ans=true;
    while(!q.empty())
    {
        string h=q.front(),ch="";
        for(int i=0;i<h.size()-1;i++)
        {
            ch+=h[i];
            if(se.find(ch)!=se.end())
            {
                string f=h.substr(i+1,h.size());
                if(se.find(f)!=se.end())
                {
                    ans=false;
                    break;
                }
                else
                {
                    se.insert(f); // dangling suffix added
                    q.push(f);
                }
            }
        }
        q.pop();
        if(!ans)
            break;
    }
    if(!ans)
        cout<<"Not Decoded uniquely\n";
    else
        cout<<"Decoded uniquely possible\n";
  return 0;
 }