• 数组构建完全二叉树


    代码:

    package com.qhong;
    
    
    import java.util.*;
    
    public class Main {
        public static void main(String[] args)   {
    
            int[] array=new int[] {0,1,2,3,4,5,6,7,8,9,10,11,12,13};
            TreeNode root=Tool.createTree(array);
            Print.PrintTreeNode(root);
        }
    }
    
    class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;
    
        TreeNode(int x) {
            val = x;
        }
    }
    
    class Tool{
        /* * 构建完全二叉树 */
        public static TreeNode createTree(int[] array){
            List<TreeNode> nodeList=new LinkedList<TreeNode>();
    
            for(int nodeIndex=0;nodeIndex<array.length;nodeIndex++){
                nodeList.add(new TreeNode(array[nodeIndex]));
            }
            for(int parentIndex=0;parentIndex<=array.length/2-1;parentIndex++){
                nodeList.get(parentIndex).left =nodeList.get(parentIndex*2+1);
                //防止是非完全二叉树
                if((parentIndex*2+2)<array.length) {
                    nodeList.get(parentIndex).right = nodeList.get(parentIndex * 2 + 2);
                }
            }
    //
    //        int lastParentIndex=array.length/2-1;
    //        nodeList.get(lastParentIndex).left =nodeList.get(lastParentIndex*2+1);
    //
    //        if(array.length%2==1){
    //            nodeList.get(lastParentIndex).right =nodeList.get(lastParentIndex*2+2);
    //        }
    
            return nodeList.get(0);
        }
    }
    
    class Print{
        //打印TreeNode
        public static void PrintTreeNode(TreeNode root){
            ArrayList arrayList=PrintFromTopToBottom(root);
            printTree(arrayList,arrayList.size());
        }
        //转换TreeNode为ArrayList
        private static ArrayList<Integer> PrintFromTopToBottom(TreeNode root) {
    
            ArrayList<Integer> list = new ArrayList();
            if(root == null)
                return list;
    
            Queue<TreeNode> queue = new LinkedList();
            queue.offer(root);
    
            while(!queue.isEmpty()){
                TreeNode treeNode = queue.poll();
                list.add(treeNode.val);
                if(treeNode.left != null)
                    queue.offer(treeNode.left);
                if(treeNode.right != null)
                    queue.offer(treeNode.right);
            }
    
            return list;
        }
    
        //以树形打印ArrayList
        private static void printTree(ArrayList array,int len){
    
            int layers = (int)Math.floor(Math.log((double)len)/Math.log((double)2))+1;  //树的层数
            int maxWidth = (int)Math.pow(2,layers)-1;  //树的最大宽度
            int endSpacing = maxWidth;
            int spacing;
            int numberOfThisLayer;
            for(int i=1;i<=layers;i++){  //从第一层开始,逐层打印
                endSpacing = endSpacing/2;  //每层打印之前需要打印的空格数
                spacing = 2*endSpacing+1;  //元素之间应该打印的空格数
                numberOfThisLayer = (int)Math.pow(2, i-1);  //该层要打印的元素总数
    
                int j;
                for(j=0;j<endSpacing;j++){
                    System.out.print("  ");
                }
    
                int beginIndex = (int)Math.pow(2,i-1)-1;  //该层第一个元素对应的数组下标
                for(j=1;j<=numberOfThisLayer;j++){
                    System.out.print(array.get(beginIndex++)+"");
                    for(int k=0;k<spacing;k++){  //打印元素之间的空格
                        System.out.print("  ");
                    }
                    if(beginIndex == len){  //已打印到最后一个元素
                        break;
                    }
                }
    
                System.out.println();
            }
            System.out.println();
        }
    
    }
                  0                              
          1              2              
      3      4      5      6      
    7  8  9  10  11  12  13  

    以后再弄二叉树就可以简单的造例子了。

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  • 原文地址:https://www.cnblogs.com/hongdada/p/6481780.html
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