Java递归、非递归实现二叉树遍历

最近找工作做笔试题发现很重要，就自己写了一点，和大家分享
import java.util.Stack;
import java.util.HashMap;
public class BinTree {
private char date;
private BinTree lchild;
private BinTree rchild;
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
public static void preOrder2(BinTree t) {
Stack<BinTree> s = new Stack<BinTree>();
while (t != null || !s.empty()) {
while (t != null) {
System.out.print(t.date);
s.push(t);
t = t.lchild;
}
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;
}