Day26

1.代码：利用栈实现先序遍历和后序遍历

/**
	 *********************
	 * Pre-order visit with stack.
	 *********************
	 */
	public void preOrderVisitWithStack() {
		ObjectStack tempStack = new ObjectStack();
		BinaryCharTree tempNode = this;
		while (!tempStack.isEmpty() || tempNode != null) {
			if (tempNode != null) {
				System.out.print("" + tempNode.value + " ");
				tempStack.push(tempNode);
				tempNode = tempNode.leftChild;
			} else {
				tempNode = (BinaryCharTree) tempStack.pop();
				tempNode = tempNode.rightChild;
			} // Of if
		} // Of while
	}// Of preOrderVisitWithStack

	/**
	 *********************
	 * Post-order visit with stack.
	 *********************
	 */
	public void postOrderVisitWithStack() {
		ObjectStack tempStack = new ObjectStack();
		BinaryCharTree tempNode = this;
		ObjectStack tempOutputStack = new ObjectStack();

		while (!tempStack.isEmpty() || tempNode != null) {
			if (tempNode != null) {
				// Store for output.
				tempOutputStack.push(new Character(tempNode.value));
				tempStack.push(tempNode);
				tempNode = tempNode.rightChild;
			} else {
				tempNode = (BinaryCharTree) tempStack.pop();
				tempNode = tempNode.leftChild;
			} // Of if
		} // Of while

		// Now reverse output.
		while (!tempOutputStack.isEmpty()) {
			System.out.print("" + tempOutputStack.pop() + " ");
		} // Of while
	}// Of postOrderVisitWithStack

main函数： 

/**
	 *********************
	 * The entrance of the program.
	 * 
	 * @param args Not used now.
	 *********************
	 */
	public static void main(String args[]) {
		BinaryCharTree tempTree = manualConstructTree();
		System.out.println("\r\nPreorder visit:");
		tempTree.preOrderVisit();
		System.out.println("\r\nIn-order visit:");
		tempTree.inOrderVisit();
		System.out.println("\r\nPost-order visit:");
		tempTree.postOrderVisit();

		System.out.println("\r\n\r\nThe depth is: " + tempTree.getDepth());
		System.out.println("The number of nodes is: " + tempTree.getNumNodes());

		tempTree.toDataArrays();
		System.out.println("The values are: " + Arrays.toString(tempTree.valuesArray));
		System.out.println("The indices are: " + Arrays.toString(tempTree.indicesArray));
		tempTree.toDataArraysObjectQueue();
		System.out.println("Only object queue.");
		System.out.println("The values are: " + Arrays.toString(tempTree.valuesArray));
		System.out.println("The indices are: " + Arrays.toString(tempTree.indicesArray));
		char[] tempCharArray = { 'A', 'B', 'C', 'D', 'E', 'F' };
		int[] tempIndicesArray = { 0, 1, 2, 4, 5, 12 };
		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();

		System.out.println("\r\nIn-order visit with stack:");
		tempTree2.inOrderVisitWithStack();
		System.out.println("\r\nPre-order visit with stack:");
		tempTree2.preOrderVisitWithStack();
		System.out.println("\r\nPost-order visit with stack:");
		tempTree2.postOrderVisitWithStack();

	}// Of main

2.运行结果：

3.总结：

a.Character是char的包装类,就像Integer和int ，包含了许多方法；

b.先序遍历的思想与中序遍历相似，后序遍历运用了两个栈，一个栈用于存储正确的输出序列，即左右根，另一个栈作为工作栈，因为根应该最后输出，且栈为后进先出，所以将根先入栈，再访问右孩子，最后访问左孩子。

c.

 我的理解：这里将结点值转化为Character类后才入栈，是以便后面直接将其pop出来？