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  1. program mountain;
  2. Uses sysutils, Math;
  3.  
  4. const
  5.     MAXN = 100005;
  6.  
  7. var
  8.     ANS, N, i, j, maxMountainLength, lung : LongInt;
  9.     P, leftLIS, rightLIS  : Array[0..MAXN-1] of LongInt;
  10.     rimossi : Ansistring;
  11.     uscita : boolean;
  12.  
  13. begin
  14.     (*assign(input,  'input.txt');  reset(input);
  15.     assign(output, 'output.txt'); rewrite(output);*)  
  16.  
  17.     ReadLn(N);
  18.     rimossi:=''; lung:=N; 
  19.     for i:=0 to N-1 do begin
  20.                         Read(P[i]);
  21.                         rimossi:=rimossi+IntTostr(P[i]);
  22.                        end;  
  23.     ReadLn();
  24.  
  25.  
  26.     ANS := 0; 
  27. 	(*leftLIS[i] stores the length of longest increasing subsequence ending at index i*)
  28. 	(*rightLIS[i] stores the length of longest decreasing subsequence starting at index i*)
  29.  
  30.    for i:=0 to  lung-1 do begin leftLIS[i]:=1; rightLIS[i]:=1; end;
  31.  
  32. 	(*Calculate LIS from left to right for each position*)
  33.  
  34.    for i := 1 to lung-1 do
  35.            for j:= 0 to i-1 do
  36.                 begin
  37.                   if (P[i] > P[j]) then leftLIS[i] := max(leftLIS[i], leftLIS[j] + 1);                          
  38.                 end;  
  39.  
  40. 	(* Calculate LIS from right to left (decreasing subsequence) for each position*)
  41.  
  42.    for i := lung - 2 downto 0 do
  43.             for  j := i + 1 to lung-1 do
  44.                begin
  45.                 if (P[i] > P[j]) then rightLIS[i] := max(rightLIS[i], rightLIS[j] + 1);                
  46. 	       end;
  47.         (* Find the maximum length of mountain subsequence*)
  48.    maxMountainLength := 0;
  49.    for i := 0 to lung-1 do
  50. 	(*A valid mountain peak must have at least one element on both sides*)
  51. 	(*leftLIS[i] > 1 ensures there's at least one element before peak*)
  52. 	(*rightLIS[i] > 1 ensures there's at least one element after peak*)
  53.    if (leftLIS[i] >= 1) and (rightLIS[i] >= 1)  then
  54.   	(*Total mountain length with peak at i Subtract 1 because peak is counted in both leftLIS and rightLIS*)
  55.          maxMountainLength := max(maxMountainLength, leftLIS[i] + rightLIS[i] - 1);
  56.  	(* Minimum removals = total elements - maximum mountain length*)
  57.    ANS:= N - maxMountainLength; 
  58.    WriteLn(ANS);
  59. end.
Success #stdin #stdout 0s 5324KB
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https://ideone.com/4p5Vsc
language:
Pascal (fpc 3.0.4)
created:
5 hours ago
visibility:
public

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