Java二叉树的建立_二叉树建树java

如果你已经知道了如何把一颗二叉树用两个数组来储存，即一个数组储存索引，一个数组储存值。那么今天在这里我们要学的是：如果给你这两个数组，你要去把它还原成一棵二叉树，并且能够实现二叉树的基本方法。

1.算法思想：

1.1我们二叉树的建立，是不是就是初始一棵二叉树？没错，就是再写一个二叉树的构造函数，不同的是初始化直接生成一棵树而非一个结点。

1.2首先他会给你两个数组，那么构造函数就应该以这两个数组为形参：

public BinaryCharTree(char[] paraDataArray, int[] paraIndicesArray)

1.3还原这可二叉树，你可以把给你的这些结点值看做是毫无关系的孤立点，我们先生成一个二叉树数组，它给你多少个结点值，那么二叉树的长度就应该有多大。由于这个二叉树数组中，每个单元的数并没有数值，其左右孩子也没有链接。我们要做的便是给这二叉树数组赋值并且链接起来。

1.4结点值直接按一个for循坏赋值就好了，关键是链接。这里需要两个for循环，采用孩子找妈妈的方法。第一个for是孩子的范围，第二个for是父亲的范围。再利用索引数组判断他们是不是父子，是则相连，不是则跳过。

for (int i = 1; i < tempNumNodes; i++) {
			for (int j = 0; j < i; j++) {
				System.out.println("indices " + paraIndicesArray[j] + " vs. " + paraIndicesArray[i]);
				if (paraIndicesArray[i] == paraIndicesArray[j] * 2 + 1) {
					tempAllNodes[j].leftChild = tempAllNodes[i];
					System.out.println("Linking " + j + " with " + i);
					break;
				} else if (paraIndicesArray[i] == paraIndicesArray[j] * 2 + 2) {
					tempAllNodes[j].rightChild = tempAllNodes[i];
					System.out.println("Linking " + j + " with " + i);
				}
			} // Of for j
		} // Of for i

1.5最后一步了，我们是从第二个结点开始，也就是孩子结点开始。根节点没有链接，最后把根节点链接上。

		value = tempAllNodes[0].value;
		leftChild = tempAllNodes[0].leftChild;
		rightChild = tempAllNodes[0].rightChild;

完整的函数：

	// 二叉树的建立
	public BinaryCharTree(char[] paraDataArray, int[] paraIndicesArray) {
		// 第一步用一顺序表储存数据
		int tempNumNodes = paraDataArray.length;
		BinaryCharTree[] tempAllNodes = new BinaryCharTree[tempNumNodes];
		for (int i = 0; i < tempNumNodes; i++) {
			tempAllNodes[i] = new BinaryCharTree(paraDataArray[i]);
		} // Of for i
 
		// 第二步，链接结点
		for (int i = 1; i < tempNumNodes; i++) {
			for (int j = 0; j < i; j++) {
				System.out.println("indices " + paraIndicesArray[j] + " vs. " + paraIndicesArray[i]);
				if (paraIndicesArray[i] == paraIndicesArray[j] * 2 + 1) {
					tempAllNodes[j].leftChild = tempAllNodes[i];
					System.out.println("Linking " + j + " with " + i);
					break;
				} else if (paraIndicesArray[i] == paraIndicesArray[j] * 2 + 2) {
					tempAllNodes[j].rightChild = tempAllNodes[i];
					System.out.println("Linking " + j + " with " + i);
				}
			} // Of for j
		} // Of for i
 
		// 第三步，第一个结点是根节点
		value = tempAllNodes[0].value;
		leftChild = tempAllNodes[0].leftChild;
		rightChild = tempAllNodes[0].rightChild;
	}// Of the second constructor

这里只是思想，你自己要运行需要补充很多地方，了解思想就好了。下面是我集成部分。

 
package datastructure.tree;
 
import java.util.Arrays;
import datastructure.queue.*;
 
/**
 ****************************
 * TODO
 * 
 * @author Chen Fan
 * @version 1.0 time 2021年12月30日
 ****************************
 */
public class BinaryCharTree {
	char value;
	BinaryCharTree leftChild;
	BinaryCharTree rightChild;
 
	// 第一个构造函数
	public BinaryCharTree(char paraName) {
		value = paraName;
		leftChild = null;
		rightChild = null;
	}// Of the constructor
 
	//
	public static BinaryCharTree manualConstructTree() {
		// 第一步构造一个根节点
		BinaryCharTree resultTree = new BinaryCharTree('a');
 
		// 第二步构造所有结点。
		BinaryCharTree tempTreeB = new BinaryCharTree('b');
		BinaryCharTree tempTreeC = new BinaryCharTree('c');
		BinaryCharTree tempTreeD = new BinaryCharTree('d');
		BinaryCharTree tempTreeE = new BinaryCharTree('e');
		BinaryCharTree tempTreeF = new BinaryCharTree('f');
		BinaryCharTree tempTreeG = new BinaryCharTree('g');
 
		// 第三步，连接所有节点
		resultTree.leftChild = tempTreeB;
		resultTree.rightChild = tempTreeC;
		tempTreeB.rightChild = tempTreeD;
		tempTreeC.leftChild = tempTreeE;
		tempTreeD.leftChild = tempTreeF;
		tempTreeD.rightChild = tempTreeG;
		return resultTree;
	}// Of manualConstructTree
 
	// 先序遍历
	public void preOrderVisit() {
		System.out.print("" + value + " ");
		if (leftChild != null) {
			leftChild.preOrderVisit();
		} // Of if
		if (rightChild != null) {
			rightChild.preOrderVisit();
		} // Of if
	}// Of preOrderVisit
 
	// 中序遍历
	public void inOrderVisit() {
		if (leftChild != null) {
			leftChild.inOrderVisit();
		} // Of if
 
		System.out.print("" + value + " ");
 
		if (rightChild != null) {
			rightChild.inOrderVisit();
		} // Of if
	}// Of inOrderVisit
 
	// 后序遍历
	public void postOrderVisit() {
		if (leftChild != null) {
			leftChild.postOrderVisit();
		} // Of if
 
		if (rightChild != null) {
			rightChild.postOrderVisit();
		} // Of if
		System.out.print("" + value + " ");
	}// Of postOrderVisit
 
	// 得到树的高度
	public int getDepth() {
		// It is a leaf
		if ((leftChild == null) && (rightChild == null)) {
			return 1;
		} // Of if
 
		// The depth of the left child.
		int tempLeftDepth = 0;
		if (leftChild != null) {
			tempLeftDepth = leftChild.getDepth();
		} // Of if
 
		// The depth of the right child.
		int tempRightDepth = 0;
		if (rightChild != null) {
			tempRightDepth = rightChild.getDepth();
		} // Of if
 
		// 树的高度选取最高的那边+1
		if (tempLeftDepth >= tempRightDepth) {
			return tempLeftDepth + 1;
		} else {
			return tempRightDepth + 1;
		} // Of if
	}// Of getDepth
 
	// 获得结点数目
	public int getNumNodes() {
		// If it is a leaf.
		if (leftChild == null && rightChild == null) {
			return 1;
		} // Of if
 
		// 左孩子的数目
		int templeftNodes = 0;
		if (leftChild != null) {
			templeftNodes = leftChild.getNumNodes();
		} // Of if
 
		// 友孩子的数目
		int tempRightNodes = 0;
		if (rightChild != null) {
			tempRightNodes = rightChild.getNumNodes();
		} // Of if
 
		// 总的节点数 = 左孩子数目 + 右孩子数目
		return templeftNodes + tempRightNodes + 1;
	}// Of getNumNodes
 
	// 根据宽度优先遍历的结点值（我称之广度数组）
	char[] valuesArray;
 
	// 完全二叉树的索引
	int[] indicesArray;
 
	public void toDataArrays() {
		// 初始化数组
		int tempLength = getNumNodes();
 
		valuesArray = new char[tempLength];
		indicesArray = new int[tempLength];
		int i = 0;
 
		// 遍历和转化同时进行
		CircleObjectQueue tempQueue = new CircleObjectQueue();
		tempQueue.enqueue(this);
		CircleIntQueue tempIntQueue = new CircleIntQueue();
		tempIntQueue.enqueue(0);
 
		BinaryCharTree tempTree = (BinaryCharTree) tempQueue.dequeue();
		int tempIntdex = tempIntQueue.dequeue();
		while (tempTree != null) {
			valuesArray[i] = tempTree.value;
			indicesArray[i] = tempIntdex;
			i++;
 
			if (tempTree.leftChild != null) {
				tempQueue.enqueue(tempTree.leftChild);
				tempIntQueue.enqueue(tempIntdex * 2 + 1);
			} // Of if
 
			if (tempTree.rightChild != null) {
				tempQueue.enqueue(tempTree.rightChild);
				tempIntQueue.enqueue(tempIntdex * 2 + 2);
			} // Of if
 
			tempTree = (BinaryCharTree) tempQueue.dequeue();
			tempIntdex = tempIntQueue.dequeue();
		} // Of while
	}// Of toDataArrays
 
	/**
	 ********************
	 * Convert the tree to data arrays, including a char array and an int array. The
	 * results are stored in two member variables.
	 * 
	 * @see #valuesArray
	 * @see #indicesArray
	 *********************
	 */
	@SuppressWarnings("removal")
	public void toDataArraysObjectQueue() {
		// Initialize arrays.
		int tempLength = getNumNodes();
 
		valuesArray = new char[tempLength];
		indicesArray = new int[tempLength];
		int i = 0;
 
		// Traverse and convert at the same time.
		CircleObjectQueue tempQueue = new CircleObjectQueue();
		tempQueue.enqueue(this);
		CircleObjectQueue tempIntQueue = new CircleObjectQueue();
		Integer tempIndexInteger = new Integer(0);
		tempIntQueue.enqueue(tempIndexInteger);
 
		BinaryCharTree tempTree = (BinaryCharTree) tempQueue.dequeue();
		int tempIndex = ((Integer) tempIntQueue.dequeue()).intValue();
		System.out.println("tempIndex = " + tempIndex);
		while (tempTree != null) {
			valuesArray[i] = tempTree.value;
			indicesArray[i] = tempIndex;
			i++;
 
			if (tempTree.leftChild != null) {
				tempQueue.enqueue(tempTree.leftChild);
				tempIntQueue.enqueue(new Integer(tempIndex * 2 + 1));
			} // Of if
 
			if (tempTree.rightChild != null) {
				tempQueue.enqueue(tempTree.rightChild);
				tempIntQueue.enqueue(new Integer(tempIndex * 2 + 2));
			} // Of if
 
			tempTree = (BinaryCharTree) tempQueue.dequeue();
			if (tempTree == null) {
				break;
			} // Of if
 
			tempIndex = ((Integer) tempIntQueue.dequeue()).intValue();
		} // Of while
	}// Of toDataArraysObjectQueue
 
	// 二叉树的建立
	public BinaryCharTree(char[] paraDataArray, int[] paraIndicesArray) {
		// 第一步用一顺序表储存数据
		int tempNumNodes = paraDataArray.length;
		BinaryCharTree[] tempAllNodes = new BinaryCharTree[tempNumNodes];
		for (int i = 0; i < tempNumNodes; i++) {
			tempAllNodes[i] = new BinaryCharTree(paraDataArray[i]);
		} // Of for i
 
		// 第二步，链接结点
		for (int i = 1; i < tempNumNodes; i++) {
			for (int j = 0; j < i; j++) {
				System.out.println("indices " + paraIndicesArray[j] + " vs. " + paraIndicesArray[i]);
				if (paraIndicesArray[i] == paraIndicesArray[j] * 2 + 1) {
					tempAllNodes[j].leftChild = tempAllNodes[i];
					System.out.println("Linking " + j + " with " + i);
					break;
				} else if (paraIndicesArray[i] == paraIndicesArray[j] * 2 + 2) {
					tempAllNodes[j].rightChild = tempAllNodes[i];
					System.out.println("Linking " + j + " with " + i);
				}
			} // Of for j
		} // Of for i
 
		// 第三步，第一个结点是根节点
		value = tempAllNodes[0].value;
		leftChild = tempAllNodes[0].leftChild;
		rightChild = tempAllNodes[0].rightChild;
	}// Of the second constructor
 
	/**
	 *********************
	 * The entrance of the program.
	 * 
	 * @param args Not used now.
	 *********************
	 */
	public static void main(String args[]) {
		char[] tempCharArray = { 'A', 'B', 'C', 'D', 'E', 'F' };
		int[] tempIndicesArray = { 0, 1, 3, 7, 15, 31 };
		System.out.println("开始建立二叉树：");
		BinaryCharTree tempTree2 = new BinaryCharTree(tempCharArray, tempIndicesArray);
 
		System.out.println("\r\nPreorder visit:");
		tempTree2.preOrderVisit();
		System.out.println("\r\nIn-order visit:");
		tempTree2.inOrderVisit();
		System.out.println("\r\nPost-order visit:");
		tempTree2.postOrderVisit();
	}// Of main
}