UVa 12471 - Association of Strings Solution

#include<iostream>
#include<list>
#include<string>
#include<cstring>
#include<sstream>
#include<cctype>
#include<string.h>
#include<algorithm>
#include<cmath>
#include<stack>
#include<fstream>
#include<cstdlib>
#include<vector>
#include<map>
#include<set>
#include<utility>
#include<iomanip>
#include<queue>

using namespace std;

#define INF (1<<29)
#define SET(a) memset(a,-1,sizeof(a))
#define ALL(a) a.begin(),a.end()
#define CLR(a) memset(a,0,sizeof(a))
#define FILL(a,v) memset(a,v,sizeof(a))
#define PB push_back
#define FOR(i,n) for(int i = 0;i<n;i++)
#define PI acos(-1.0)
#define EPS 1e-9
#define MP(a,b) make_pair(a,b)
#define min3(a,b,c) min(a,min(b,c))
#define max3(a,b,c) max(a,max(b,c))
#define READ(f) freopen(f, "r", stdin)
#define WRITE(f) freopen(f, "w", stdout)
#define LL long long
#define MX 100010
#define MOD 1000000007

int failur[MX],length;
char pattern[MX];

void FailureFunction(int i,int j)
{
    while(i<length)
    {
        if(pattern[i]==pattern[j])
        {
            j++;
            failur[i]=j;
            i++;
        }
        else if(j>0)
            j=failur[j-1];
        else
        {
            failur[i]=0;
            i++;
        }
    }
}


int main()
{
    int t,kk=1,n,arr[MX];
    bool found,chk;
    cin>>t;
    while(t--)
    {
        cin>>n;
        for(int i=0;i<n;i++)
            cin>>arr[i];

        if(arr[0]!=0)
            {
                cout<<"Case "<<kk++<<": -1"<<endl;
                continue;
            }
        chk=true;
        failur[0]=0;
        length=1;
        pattern[0]='a';
        for(int i=1;i<n;i++)
        {
            length=i+1;
            found=false;
            for(int j=0;j<16;j++)
            {
                pattern[i]=j+'a';
                FailureFunction(i, failur[i-1]);
                if(failur[i]==arr[i])
                    {
                        found=true;
                        break;
                    }
            }
            if(!found)
                {
                    chk=false;
                    break;
                }
        }

        if(!chk)
            cout<<"Case "<<kk++<<": -1"<<endl;
        else
            {
                cout<<"Case "<<kk++<<": ";
                for(int i=0;i<n;i++)
                    cout<<pattern[i];
                cout<<endl;
            }

    }
return 0;
}