105 lines
3 KiB
Java
105 lines
3 KiB
Java
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import java.util.ArrayList;
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import java.util.List;
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/*
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* * Data Structures & Algorithms 6th Edition
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* Goodrich, Tamassia, Goldwasser
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* Code Fragments 8.2-8.5, 8.19-21
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*\
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/*
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* an abstract base class providing some functionality of the tree interface.
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* @author Gabriel Venberg
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*/
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public abstract class AbstractTree<E> implements Tree<E> {
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public boolean isInternal(Position<E> p) {return numChildren(p)>0;}
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public boolean isExternal(Position<E> p){return numChildren(p)==0;}
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public boolean isRoot(Position<E> p){return p == root();}
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public boolean isEmpty(){return size()==0;}
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/**returns the number of levels sperating position p from the root.*/
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public int depth(Position<E> p){
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if (isRoot(p)){return 0;}
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else{return 1+depth(parent(p));}
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}
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/**returns the hight of the tree.*/
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private int hightBad(){ //works, but quadratic worst case time.
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int h=0;
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for(Position<E> p : positions()){
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//only consider leaf positions.
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if(isExternal(p)){h=Math.max(h, depth(p));}
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}
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return h;
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}
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/**returns the hight of the subtree rooted at position p.*/
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public int hight(Position<E> p){
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//base case if p is external
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int h=0;
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for (Position<E> c : children(p)){
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h=Math.max(h,1+hight(c));
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}
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return h;
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}
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//iterators
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/**adds positions of the subtree rooted at position p to the given snapshot (for use in traversal)*/
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private void preorderSubtree(Position<E> p, List<Position<E>> snapshot){
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//for preorder, add position p before exploring subtrees.
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snapshot.add(p);
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for(Position<E> c:children(p)){
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preorderSubtree(c, snapshot);
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}
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}
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/**returns an iterable collection of positions in the tree, reported in preorder*/
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public Iterable<Position<E>> preorder(){
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List<Position<E>> snapshot=new ArrayList<>();
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//fill the snapshot recursively
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if(!isEmpty()){
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preorderSubtree(root(), snapshot);
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}
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return snapshot;
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}
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/**adds positions of the subtree rooted at position p to the given snapshot (for use in traversal)*/
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private void postorderSubtree(Position<E> p, List<Position<E>> snapshot){
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//for postorder, add position p before exploring subtrees.
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for(Position<E> c:children(p)){
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postorderSubtree(c, snapshot);
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}
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snapshot.add(p);
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}
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/**returns an iterable collection of positions in the tree, reported in postorder*/
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public Iterable<Position<E>> postorder(){
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List<Position<E>> snapshot=new ArrayList<>();
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//fill the snapshot recursively
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if(!isEmpty()){
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postorderSubtree(root(), snapshot);
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}
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return snapshot;
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}
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/**returns an iterable collection of positions in the tree in breadth first traversal*/
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public Iterable<Position<E>> breadthFirst(){
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List<Position<E>> snapshot=new ArrayList<>();
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if(!isEmpty()){
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Queue<Position<E>> fringe=new LinkedQueue<>();
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fringe.enqueue(root());
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while(!fringe.isEmpty()){
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Position<E> p=fringe.dequeue();
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snapshot.add(p);
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for(Position<E> c:children(p)){
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fringe.enqueue(c);
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}
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}
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}
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return snapshot;
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}
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/**default iterator*/
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public Iterable<Position<E>> positions(){return preorder();}
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}
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