Priority Queue (heap)

In the case of printer jobs, the queue is generally used in the form of FIFO (fisrt in first out), but when encountering a 1-part and a 100-part job, it is relatively reasonable to print 1 copies, in addition, the priority of different jobs is different, priority should be processed first.

Insert = = Enqueue

Deletemin = = Dequeue

Binary heap (complete binary tree): In addition to the bottom layer, a fully filled two-tree, the underlying elements from left to right fill in.

A fully binary tree is a regular, usable array representation: for any node element x, its parent node element H->ELEMENT[I/2], its left son H->element[2i], right son h->element[2i+1].

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A heap of data structures: an array, a capacity, and the current heap size.

Precautions:

Node declaration:

struct heap{       int           capacity;        int            size;       ElementType   *elements;}

Heap order: The keyword of node x is greater than or equal to the keyword of node x Father node.

Priority Queue creat:

Priorityqueue *initialize (intmaxelement) {Priotityqueue*H; if(Maxelement <minpqsize) {cout<<"Priorityqueue is too small"<<Endl; returnNULL; } H->elements = New Element[maxelement +1]; if(H->elements = =NULL) {cout<<"Out of space"<<Endl; returnNULL; } H->capacity =maxelement; H->size =0; H->elements[0] =Mindata;//mindata is a small enough number to ensure that the element is inserted up to i=1 at the root node. returnH;}

Insert: (end insert)

voidInsert (ElementType X, Priotityqueue *H) {       if(Isfull (H)) {cout<<"Out of space"<<Endl; return; }        for(inti = ++h->size; X < h->elements[i/2]; I/=2)//h->elements[0] is a small enough number mindata to ensure that the x<mindata is not established. H->elements[i] = h->elements[i/2]; H->elements[i] =X;}

Deletemin (deleted at root)

ElementType Deletemin (Priorityqueue *i) {       intChild ;       ElementType minelement, lastelement; if(IsEmpty (H)) {cout<<"Priotityqueue is empty"<<Endl; returnh->elements[0]; } minelement= h->elements[1]; Lastelement= h->elements[h->size--];//Save the last element, Size-1                  for(inti =1;2*i <= h->size; i =Child ) { Child=2*i; if(Child! = h->size && H->element[child +1] < h->Element[child]) child++; if(h->element[child]<lastelement) H->element[i] = h->Element[child]; Else                  Break; } H->elements[i] =lastelement; returnminelement;}

Priority Queue (heap)