ENG  RUSTimus Online Judge
Online Judge
Problems
Authors
Online contests
About Online Judge
Frequently asked questions
Site news
Webboard
Links
Problem set
Submit solution
Judge status
Guide
Register
Update your info
Authors ranklist
Current contest
Scheduled contests
Past contests
Rules
back to board

Discussion of Problem 1423. String Tale

Wong answer#16! What's wrong?
Posted by PanYe 11 Aug 2006 09:19
Program KMP;

Const
  Maxn=250000;

Var
  i,j,n,k,l,ans:Longint;
  S,T:ansistring;
  Next:array[0..Maxn] of Longint;

Begin
  Readln(N);
  Readln(S);
  Readln(T);
  S:=S+S;
  Next[0]:=0;Next[1]:=0;k:=0;
  For i:=2 to length(T) Do
    Begin
      While (k>0) And (T[i]<>T[k+1]) Do
        K:=Next[k];
      If (T[i]=T[k+1]) Then Inc(K);
      Next[i]:=k;
    End;
  I:=1;j:=1;
  While I<=length(S) Do
    Begin
      L:=I;
      While (i<=2*n) And (j<=n) And (S[I]=T[J]) Do
        Begin
          Inc(i);Inc(J);
        End;
      Ans:=i-n;
      If J=n+1 Then Break;
      If J=1 Then I:=L+1 Else I:=L+J-1-Next[j-1];
      J:=Next[J-1]+1;
    End;
  l:=Ans;
  If n-l+1=n Then Writeln(0) Else If i>length(S) Then Writeln(-1) Else Writeln(n-l+1);
  End.
Re: Wong answer#16! What's wrong?
Posted by Lomir 21 Jan 2007 23:06
Solving this problem I was caught by all triky tests (WA6, WA8, WA16).

So test 16 is something like this:
6
aabaaa
aaabaa

Answer is: 1
Your program, like mine at first, would output 5, i think.