bzoj2151: Planting trees (doubly linked list + heap)

The main idea: N number around a circle, select a number can not choose its adjacent two number, asked to choose the number of M, the maximum value is how much.

The maximum number of n is maintained with the heap first, each time the maximum value added to the answer, select a number after it is possible to choose it adjacent two better than him, so the next two number is deleted, the number of the selected value to the left of the number + the number on the right-the number of the election, if the next time the number is not selected to replace this number for another two, Select M to take the m number. A number of the left and right sides of the number of the two-way linked list to do it.

The code is as follows:

varN,m,x,i,ans:longint; L,r,heap,pos,a:Array[0..200001] ofLongint;procedureDown (i:longint);varT,j:longint;begin   while(i<<1<=n) Do  begin    if(i<<1=n)or(a[heap[i<<1]]>a[heap[i<<1 or 1]]) Thenj:=i<<1    Elsej:=i<<1 or 1; ifA[HEAP[I]]&LT;A[HEAP[J]] Then    beginT:=heap[i];heap[i]:=heap[j];heap[j]:=T; T:=pos[heap[i]];p Os[heap[i]]:=pos[heap[j]];p os[heap[j]]:=T; I:=J; End    Elseexit; End;End;procedureUp (i:longint);varT:longint;begin   whileI>1  Do  begin    ifA[heap[i]]>a[heap[i>>1]] Then    beginT:=heap[i];heap[i]:=heap[i>>1];heap[i>>1]:=T; T:=pos[heap[i]];p os[heap[i]]:=pos[heap[i>>1]];p os[heap[i>>1]]:=T; I:=i>>1; End    Elseexit; End;End; beginreadln (n,m); if(m>n>>1) ThenWriteln ('error!')  Else  begin     fori:=1  toN Do    beginread (a[i]); L[i]:=i-1; r[i]:=i+1; heap[i]:=i;pos[i]:=i;up (i); End; l[1]:=n;r[n]:=1;  fori:=1  toM Do    beginx:=heap[1];inc (ans,a[x]); A[X]:=a[l[x]]+a[r[x]]-A[x];d own (pos[x]); A[L[X]]:=-maxlongint;down (Pos[l[x]); l[x]:=L[l[x]]; A[R[X]]:=-maxlongint;down (Pos[r[x]); r[x]:=R[r[x]]; L[R[X]]:=x;r[l[x]]:=x; End;  Writeln (ANS); End;End.

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PS: I know the heap can be taken to delete elements Qaq

bzoj2151: Planting trees (doubly linked list + heap)