创建二叉树:层次遍历--树的宽度高度,后序遍历--祖先节点

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创建二叉树,遍历二叉树.详细介绍了层次遍历和后序遍历的应用.
层次遍历:树的高度,树的宽度,每一层节点个数等
后序遍历:根节点到某节点的路径,两个节点的最近公共祖先等
package tree;import java.util.LinkedList;import java.util.Queue;import java.util.Stack;public class TreeADT {    private String data=null;      private TreeADT  leftChild=null;      private TreeADT  rightChild=null;          public TreeADT (String data){        this.data=data;          this.leftChild=null;          this.rightChild=null;      }      //创建一颗二叉树    public void createBinTree(TreeADT  root){      TreeADT  newNodeB = new TreeADT ("B");          TreeADT  newNodeC = new TreeADT ("C");          TreeADT  newNodeD = new TreeADT ("D");          TreeADT  newNodeE = new TreeADT ("E");          TreeADT newNodeF = new TreeADT ("F");          newNodeF.rightChild=new TreeADT("G");        root.leftChild=newNodeB;          root.rightChild=newNodeC;          root.leftChild.leftChild=newNodeD;          root.leftChild.rightChild=newNodeE;          root.rightChild.rightChild=newNodeF;      }      //访问节点数据    public void visted(TreeADT subTree){           System.out.println(subTree.data);;          }    //前序递归遍历    public void preOrder(TreeADT subTree){           if(subTree!=null){                  visted(subTree);                  preOrder(subTree.leftChild);                  preOrder(subTree.rightChild);              }          }    //非递归,前序遍历.    public void noPreOrder(TreeADT subTree){         Stack <TreeADT>stack=new Stack<TreeADT>();         TreeADT p=subTree;         while(!stack.empty()||p!=null){             if(p!=null){                 visted(p);                 stack.push(p);                 p=p.leftChild;             }             else{                 p=stack.pop();                 p=p.rightChild;             }         }     }    //递归中序遍历    public void inOrder(TreeADT subTree){        if(subTree!=null){            inOrder(subTree.leftChild);            visted(subTree);            inOrder(subTree.rightChild);        }    }    //非递归中序遍历    public void noInOrder(TreeADT subTree){        Stack<TreeADT> stack=new Stack<TreeADT>();        TreeADT p=subTree;        while(p!=null||!stack.empty()){            if(p!=null){                stack.push(p);                p=p.leftChild;            }            else{                p=stack.pop();                visted(p);                p=p.rightChild;            }        }    }    //递归后序遍历    public void postOrder(TreeADT subTree){        if(subTree!=null){            postOrder(subTree.leftChild);            postOrder(subTree.rightChild);            visted(subTree);        }    }    //非递归后序遍历    public void noPostOrder(TreeADT subTree){        Stack<TreeADT>stack=new Stack<TreeADT>();        TreeADT p=subTree;        TreeADT r=null;        while(p!=null||!stack.empty()){            if(p!=null){                stack.push(p);                p=p.leftChild;            }            else{                p=stack.peek();                if(p.rightChild!=null&&p.rightChild!=r){                    p=p.rightChild;                    stack.push(p);                    p=p.leftChild;                }                else{                    p=stack.pop();                    visted(p);                    r=p;                    p=null;                }            }        }    }    //层次遍历    public void levelOrder(TreeADT subtree){        TreeADT p=subtree;        Queue <TreeADT>queue=new  LinkedList<TreeADT>();//接口不能直接实例化，需要对象上转型;queue是个接口，而stack是个类。。        queue.add(p);        while(!queue.isEmpty()){            p=queue.remove();//一定要保存队列的指针            visted(p);            if(p.leftChild!=null) queue.add(p.leftChild);            if(p.rightChild!=null) queue.add(p.rightChild);        }    }     //非递归实现树的高度    public void  high(TreeADT subTree){        int front=0;int rear=0;TreeADT[] Q=new TreeADT [20];int last=1;int level=0;        TreeADT p=subTree;        Q[++rear]=p;        while(front<rear){            p=Q[++front];            if(p.leftChild != null){                Q[++rear]=p.leftChild;            }            if(p.rightChild!=null){                Q[++rear]=p.rightChild;            }            if(front==last){                level++;                last=rear;            }        }        System.out.println(level);    }    //非递归实现求树的每一层宽度    public void len(TreeADT subTree){        int front=0,rear=0,level=0,last=1,count[]=new int [10];TreeADT[]Q=new TreeADT[20];        count[0]=1;        TreeADT p=subTree;        Q[++rear]=p;        while(front<rear){            p=Q[++front];            if(p.leftChild!=null) {Q[++rear]=p.leftChild;count[level+1]++;}            if(p.rightChild!=null){Q[++rear]=p.rightChild;count[level+1]++;}            if(front==last){                level++;                last=rear;            }        }        for(int i=0;i<level;i++){            System.out.println(count[i]);        }    }    //递归实现树的高度和宽度    public int  iteratorHigh(TreeADT subTree){        TreeADT p=subTree;        if(p==null){            return 0;        }        else return  iteratorHigh(p.leftChild)>iteratorHigh(p.rightChild)?1+iteratorHigh(p.leftChild):1+iteratorHigh(p.rightChild);    }    public static void main(String[] args) {// TODO Auto-generated method stub        TreeADT  root =new TreeADT ("A");        root.createBinTree(root);        //root.inOrder(root);        //root.noInOrder(root);       //root.postOrder(root);        //root.noPostOrder(root);        root.levelOrder(root);}}
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