package com.nowcoder.校招真题2016;
import java.util.Stack;
import java.util.HashMap;
public class BinTree {
//二叉树的三个属性;
private char date; //节点值
private BinTree lchild; //左子树
private BinTree rchild; //右子树
public BinTree(char c) {
date = c;
}
// 先序遍历递归
public static void preOrder(BinTree t) {
if (t == null) {
return;
}
System.out.print(t.date);
preOrder(t.lchild);
preOrder(t.rchild);
}
// 中序遍历递归
public static void InOrder(BinTree t) {
if (t == null) {
return;
}
InOrder(t.lchild);
System.out.print(t.date);
InOrder(t.rchild);
}
// 后序遍历递归
public static void PostOrder(BinTree t) {
if (t == null) {
return;
}
PostOrder(t.lchild);
PostOrder(t.rchild);
System.out.print(t.date);
}
// 先序遍历非递归
A
B C
D E F G
H I J K L M N O
遍历顺序 ABDH ->I->E ->J->K->C->F->L->M->G->N->O
public static void preOrder2(BinTree t) {
Stack<BinTree> s = new Stack<BinTree>();
while (t != null || !s.empty()) { //第一次运行时 t !=null s.empty()成立
while (t != null) {
System.out.print(t.date);
s.push(t); // 将T对象压入栈内
t = t.lchild; 将这个的左子树赋值给 T, 不停的循环并将左子树的节点压入到栈内,最后遍历到最后一个左子树
}
if (!s.empty()) {
t = s.pop(); //
t = t.rchild;
}
}
}
// 中序遍历非递归
public static void InOrder2(BinTree t) {
Stack<BinTree> s = new Stack<BinTree>();
while (t != null || !s.empty()) {
while (t != null) {
s.push(t);
t = t.lchild;
}
if (!s.empty()) {
t = s.pop();
System.out.print(t.date);
t = t.rchild;
}
}
}
// 后序遍历非递归
public static void PostOrder2(BinTree t) {
Stack<BinTree> s = new Stack<BinTree>();
Stack<Integer> s2 = new Stack<Integer>();
Integer i = new Integer(1);
while (t != null || !s.empty()) {
while (t != null) {
s.push(t);
s2.push(new Integer(0));
t = t.lchild;
}
while (!s.empty() && s2.peek().equals(i)) {
s2.pop();
System.out.print(s.pop().date);
}
if (!s.empty()) {
s2.pop();
s2.push(new Integer(1));
t = s.peek();
t = t.rchild;
}
}
}
public static void main(String[] args) {
BinTree b1 = new BinTree('a');
BinTree b2 = new BinTree('b');
BinTree b3 = new BinTree('c');
BinTree b4 = new BinTree('d');
BinTree b5 = new BinTree('e');
/**
* a
* / /
* b c
* / /
* d e
*/
b1.lchild = b2;
b1.rchild = b3;
b2.lchild = b4;
b2.rchild = b5;
BinTree.preOrder(b1);
System.out.println();
BinTree.preOrder2(b1);
System.out.println();
BinTree.InOrder(b1);
System.out.println();
BinTree.InOrder2(b1);
System.out.println();
BinTree.PostOrder(b1);
System.out.println();
BinTree.PostOrder2(b1);
}
}