温故而知新-二叉树遍历

温故而知新-二叉树遍历

本文主要介绍 二叉树的深度优先遍历及广度优先遍历：

• BinaryTree

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public class BinaryTree{
    static class TreeNode{
        int value;
        TreeNode left;
        TreeNode right;

        TreeNode(int value){
            this.value = value;
        }
    }

    TreeNode root ;
    public BinaryTree(int[] array){
        root = makeBinaryTree(array,1);
    }
    public TreeNode makeBinaryTree(int[] array,int index){
        if(index < array.length){
            int value = array[index];
            if(value != 0){
                TreeNode t = new TreeNode(value);
                array[index] = 0;
                t.left = makeBinaryTree(array,index*2);
                t.right = makeBinaryTree(array,index*2+1);
                return t;
            }
        return null;
    }   

    public void depthOrderTraversal(){
        if(root == null){
            System.out.print("root is empty");
        }
        ArrayDeque stack = new ArrayDeque();
        stack.push(root);
        while(stack.isEmpty == false){
            TreeNode t = stack.pop();
            if(t.left != null){
                stack.push(t.left);
            }
            if(t.right != null){
                stack.push(t.right);
            }
        }
        System.out.print("  /n");
    }

    public void levelOrderTravesal(){
        if(root == null){
            System.out.print("root is empty");
        }
        ArrayDeque queue = new ArrayDeque();
        queue.add(root);
        while(queue.isEmpty == false){
            TreeNode t= queue.remove();
            if(t.left != null ){
                queue.add(t.left);
            }
            if(t.right != null){
                queue.add(t.right);
            }
        }
        System.out.print("/n");
    }
}

public static void main(String[] arg){
    int[] array={0,13,65,5,97,25,0,37,22,0,4,28,0,0,32,0};
    BinaryTree tree = new BinaryTree(array);
    tree.dethOrderTraversal();
    tree.levelOrderTraversal();
}

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深度优先遍历与广度优先遍历算法在面试过程中为必考算法，为java基础部分。