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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,h, maxMountainLength, lung : LongInt;
  9.     P, leftLIS, rightLIS  : Array[0..MAXN-1] of LongInt;
  10.     rimossi : Ansistring;
  11.  
  12. begin
  13.      (*assign(input,  'input.txt');  reset(input);
  14.     assign(output, 'output.txt'); rewrite(output);*)
  15.     ReadLn(N);
  16.     rimossi:=''; lung:=N;
  17.     for i:=0 to N-1 do begin
  18.                         Read(P[i]);
  19.                         rimossi:=rimossi+IntTostr(P[i]);
  20.                        end;  
  21.     ReadLn();
  22.     h:=1;
  23.     while h<1001 do 
  24.        begin
  25.         i:=2; 
  26.         while i<lung do
  27.               begin
  28.                 if  (rimossi[i]<rimossi[i-1]) and (rimossi[i]<rimossi[i+1]) then
  29.                                                                               begin
  30.                                                                                 delete(rimossi,i,1);
  31.                                                                                 lung:=lung-1;
  32.  
  33.                                                                               end;
  34.               i:=i+1;
  35.               end;
  36.            h:=h+1;   
  37.       end;     
  38.     for i:=1 to lung  do P[i-1]:=StrToInt(rimossi[i]); 
  39.  
  40.     ANS := 0; 
  41. 	(*leftLIS[i] stores the length of longest increasing subsequence ending at index i*)
  42. 	(*rightLIS[i] stores the length of longest decreasing subsequence starting at index i*)
  43.  
  44.    for i:=0 to  lung-1 do begin leftLIS[i]:=1; rightLIS[i]:=1; end;
  45.  
  46. 	(*Calculate LIS from left to right for each position*)
  47.  
  48.    for i := 1 to lung-1 do
  49.            for j:= 0 to i-1 do
  50.                 begin
  51.                   if (P[i] > P[j]) then leftLIS[i] := max(leftLIS[i], leftLIS[j] + 1);                          
  52.                 end;  
  53.  
  54. 	(* Calculate LIS from right to left (decreasing subsequence) for each position*)
  55.  
  56.    for i := lung - 2 downto 0 do
  57.             for  j := i + 1 to lung-1 do
  58.                begin
  59.                 if (P[i] > P[j]) then rightLIS[i] := max(rightLIS[i], rightLIS[j] + 1);                
  60. 	       end;
  61.         (* Find the maximum length of mountain subsequence*)
  62.    maxMountainLength := 0;
  63.    for i := 0 to lung-1 do
  64. 	(*A valid mountain peak must have at least one element on both sides*)
  65. 	(*leftLIS[i] > 1 ensures there's at least one element before peak*)
  66. 	(*rightLIS[i] > 1 ensures there's at least one element after peak*)
  67.    if (leftLIS[i] >= 1) and (rightLIS[i] >= 1)  then
  68.   	(*Total mountain length with peak at i Subtract 1 because peak is counted in both leftLIS and rightLIS*)
  69.          maxMountainLength := max(maxMountainLength, leftLIS[i] + rightLIS[i] - 1);
  70.  	(* Minimum removals = total elements - maximum mountain length*)
  71.    ANS:= N - maxMountainLength; 
  72.    WriteLn(ANS);
  73. end.
  74.  
Success #stdin #stdout 0s 5288KB
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https://ideone.com/Tv4DPC
language:
Pascal (fpc 3.0.4)
created:
2 hours ago
visibility:
public

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