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  1. // nongdanjohn - THPTNguyen-Quang-Dieu
  2. const maxN = 100001;
  3. var N: longint;
  4.     A: array[1..maxN] of longint;
  5.     Link,Head: array[1..maxN] of longint;
  6.     Free: array[1..maxN] of boolean;
  7.  
  8. Procedure Enter;
  9. var i: longint;
  10. begin
  11.     Readln(N);
  12.     For i:=1 to N do Read(A[i]);
  13.     For i:=N downto 1 do
  14.       if Free[A[i]] then
  15.         begin
  16.           Head[A[i]]:=i;
  17.           Link[i]:=i;
  18.           Free[A[i]]:=False;
  19.         end else
  20.         begin
  21.           link[i]:=head[A[i]];
  22.           Head[A[i]]:=i;
  23.         end;
  24. end;
  25.  
  26. Procedure Sort(L,H: longint);
  27. var i,j,k,t: longint;
  28. begin
  29.     i:=l; j:=h; k:=A[(l+h) div 2];
  30.     repeat
  31.       while A[i]<k do inc(i);
  32.       while A[j]>k do dec(j);
  33.       if i<=j then
  34.         begin
  35.           t:=A[i]; A[i]:=A[j]; A[j]:=t;
  36.           inc(i); dec(j);
  37.         end;
  38.     until i>j;
  39.     if l<j then sort(l,j);
  40.     if i<h then sort(i,h);
  41. end;
  42.  
  43. procedure solve;
  44. var i,j,res: longint;
  45. begin
  46.     Fillchar(Free, sizeof(Free), true);
  47.     res:=0;
  48.     for i:=1 to n do
  49.       begin
  50.         j:=head[A[i]];
  51.         if Free[j] then
  52.           begin
  53.             inc(res);
  54.             Free[j]:=False; Free[j+1]:=False; Free[j-1]:=False;
  55.           end;
  56.         head[A[i]]:=Link[j];
  57.       end;
  58.     Writeln(Res);
  59. end;
  60.  
  61. Begin
  62.     Assign(Input,''); Reset(Input);
  63.     Enter;
  64.     Sort(1,n);
  65.     solve;
  66. End.
Success #stdin #stdout 0s 1544KB
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https://ideone.com/GEwRcb
language:
Pascal (fpc 3.0.4)
created:
9 years ago
visibility:
secret

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