# UVa: 11512 – GATTACA

Solution Idea: Build Suffix array and LCP array then answer is the maximum entry in LCP array.

Lesson: Always use a ‘\$’ Symbol in this implementation of Suffix Array. Otherwise you will get nothing but WA -_- .

```
#include &lt;bits/stdc++.h&gt;

#define pii              pair &lt;int,int&gt;
#define pll              pair &lt;long long,long long&gt;
#define sc               scanf
#define pf               printf
#define Pi               2*acos(0.0)
#define ms(a,b)          memset(a, b, sizeof(a))
#define pb(a)            push_back(a)
#define MP               make_pair
#define db               double
#define ll               long long
#define EPS              10E-10
#define ff               first
#define ss               second
#define sqr(x)           (x)*(x)
#define D(x)             cout&lt;&lt;#x &quot; = &quot;&lt;&lt;(x)&lt;&lt;endl
#define VI               vector &lt;int&gt;
#define DBG              pf(&quot;Hi\n&quot;)
#define MOD              1000000007
#define CIN              ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define SZ(a)            (int)a.size()
#define sf(a)            scanf(&quot;%d&quot;,&amp;a)
#define sfl(a)           scanf(&quot;%lld&quot;,&amp;a)
#define sff(a,b)         scanf(&quot;%d %d&quot;,&amp;a,&amp;b)
#define sffl(a,b)        scanf(&quot;%lld %lld&quot;,&amp;a,&amp;b)
#define sfff(a,b,c)      scanf(&quot;%d %d %d&quot;,&amp;a,&amp;b,&amp;c)
#define sfffl(a,b,c)     scanf(&quot;%lld %lld %lld&quot;,&amp;a,&amp;b,&amp;c)
#define stlloop(v)       for(__typeof(v.begin()) it=v.begin();it!=v.end();it++)
#define loop(i,n)        for(int i=0;i&lt;n;i++)
#define loop1(i,n)       for(int i=1;i&lt;=n;i++)
#define REP(i,a,b)       for(int i=a;i&lt;b;i++)
#define RREP(i,a,b)      for(int i=a;i&gt;=b;i--)
#define TEST_CASE(t)     for(int z=1;z&lt;=t;z++)
#define PRINT_CASE       printf(&quot;Case %d: &quot;,z)
#define LINE_PRINT_CASE  printf(&quot;Case %d:\n&quot;,z)
#define CASE_PRINT       cout&lt;&lt;&quot;Case &quot;&lt;&lt;z&lt;&lt;&quot;: &quot;
#define all(a)           a.begin(),a.end()
#define intlim           2147483648
#define infinity         (1&lt;&lt;28)
#define ull              unsigned long long
#define gcd(a, b)        __gcd(a, b)
#define lcm(a, b)        ((a)*((b)/gcd(a,b)))

using namespace std;

/*----------------------Graph Moves----------------*/
//const int fx[]={+1,-1,+0,+0};
//const int fy[]={+0,+0,+1,-1};
//const int fx[]={+0,+0,+1,-1,-1,+1,-1,+1};   // Kings Move
//const int fy[]={-1,+1,+0,+0,+1,+1,-1,-1};  // Kings Move
//const int fx[]={-2, -2, -1, -1,  1,  1,  2,  2};  // Knights Move
//const int fy[]={-1,  1, -2,  2, -2,  2, -1,  1}; // Knights Move
/*------------------------------------------------*/

//int Set(int N,int pos){return N=N | (1&lt;&lt;pos);}
//int reset(int N,int pos){return N= N &amp; ~(1&lt;&lt;pos);}
//bool check(int N,int pos){return (bool)(N &amp; (1&lt;&lt;pos));}
/*------------------------------------------------*/

#define mx 100005

int SA[mx],tempSA[mx];
int RA[mx],tempRA[mx];
int count_sort[mx];
char str[mx],pattern[mx];

int Phi[mx],LCP[mx],PLCP[mx];

int n;

void counting_sort(int k)
{
ms(count_sort,0);
int maxi=max(300,n);
for(int i=0; i&lt;n; i++)
{
int a=i+k&lt;n?RA[i+k]:0;
count_sort[a]++;
}
for(int i=0,sum=0; i&lt;maxi; i++)
{
int x=count_sort[i];
count_sort[i]=sum;
sum+=x;
}

for(int i=0; i&lt;n; i++)
{
int a=SA[i]+k&lt;n?RA[SA[i]+k]:0;
int b=count_sort[a];
count_sort[a]++;
tempSA[b]=SA[i];
}

for(int i=0; i&lt;n; i++)
SA[i]=tempSA[i];

}

void build_Suffix_Array()
{
for(int i=0; i&lt;n; i++)
{
RA[i]=str[i];
SA[i]=i;
}
for(int k=1; k&lt;n; k*=2)
{
counting_sort(k);
counting_sort(0);
int r;
tempRA[SA[0]]=r=0;
for(int i=1; i&lt;n; i++)
{
if(RA[SA[i]]==RA[SA[i-1]] &amp;&amp; RA[SA[i]+k]==RA[SA[i-1]+k])
tempRA[SA[i]]=r;
else
tempRA[SA[i]]=++r;
}
for(int i=0; i&lt;n; i++)
RA[i]=tempRA[i];
if(RA[SA[n-1]]==n-1) break;
}
}

void compute_LCP()
{
int l=0;
Phi[SA[0]]=-1;
for(int i=1; i&lt;n; i++)
Phi[SA[i]]=SA[i-1];
for(int i=0,L=0; i&lt;n; i++)
{
if(Phi[i]==-1)
{
PLCP[i]=0;
continue;
}
while(str[i+L]==str[Phi[i]+L])
{
//            D(str[i+L]);
//            D(str[Phi[i]+L]);
L++;
}
PLCP[i]=L;
L=max(L-1,0);
}

for(int i=0; i&lt;n; i++)
LCP[i]=PLCP[SA[i]];

}

int find_pattern(int len)
{
int lo=0,hi=n-1;
while(lo&lt;hi)
{
int mid=(lo+hi)/2;
int res=strncmp(str+SA[mid],pattern,len);
if(res&gt;=0) hi=mid;
else
lo=mid+1;
}
ll ret=lo;
if(strncmp(str+SA[ret],pattern,len)!=0) return 0;
lo=0,hi=n-1;
while(lo&lt;hi)
{
int mid=(lo+hi)/2;
int res=strncmp(str+SA[mid],pattern,len);
if(res&gt;0) hi=mid;
else
lo=mid+1;
}

if(strncmp(str+SA[hi],pattern,len)!=0) hi--;
return hi-ret+1;
}

int main()
{

//    freopen(&quot;in.txt&quot;,&quot;r&quot;,stdin);
//	  freopen(&quot;out.txt&quot;,&quot;w&quot;,stdout);

int t;
sf(t);
TEST_CASE(t)
{
scanf(&quot;%s&quot;,str);
strcat(str,&quot;\$&quot;);
n=strlen(str);
string str1=str;
build_Suffix_Array();
//        for(int i=0; i&lt;n; i++)
//            pf(&quot;%d\n&quot;,SA[i]);
compute_LCP();

//        for(int i=0; i&lt;n; i++)
//            cout&lt;&lt;SA[i]&lt;&lt;&quot; &quot;;
//        cout&lt;&lt;endl;
//        for(int i=0; i&lt;n; i++)
//            cout&lt;&lt;LCP[i]&lt;&lt;&quot; &quot;;
//        cout&lt;&lt;endl;

int ans=0;
for(int i=0; i&lt;n; i++)
ans=max(ans,LCP[i]);
if(ans&lt;=0)
{
pf(&quot;No repetitions found!\n&quot;);
continue;
}
int cnt=0,pos=0;
for(int i=0; i&lt;n; i++)
{
if(LCP[i]==ans)
{
pos=i;
break;
}
}

strncpy(pattern,str+SA[pos],ans);

cnt=find_pattern(ans);

printf(&quot;%s %d\n&quot;,str1.substr(SA[pos],ans).c_str(),cnt);

}

return 0;
}

```