二叉树的遍历（递归、非递归）

 1 public class BinTree {
 2     private char date;
 3     private BinTree lchild;
 4     private BinTree rchild;
 5
 6     public BinTree(char c) {
 7         date = c;
 8     }
 9
10     // 先序遍历递归
11     public static void preOrder(BinTree t) {
12         if (t == null) {
13             return;
14         }
15         System.out.print(t.date);
16         preOrder(t.lchild);
17         preOrder(t.rchild);
18     }
19
20     // 中序遍历递归
21     public static void InOrder(BinTree t) {
22         if (t == null) {
23             return;
24         }
25         InOrder(t.lchild);
26         System.out.print(t.date);
27         InOrder(t.rchild);
28     }
29
30     // 后序遍历递归
31     public static void PostOrder(BinTree t) {
32         if (t == null) {
33             return;
34         }
35         PostOrder(t.lchild);
36         PostOrder(t.rchild);
37         System.out.print(t.date);
38     }
39
40     // 先序遍历非递归
41     public static void preOrder2(BinTree t) {
42         Stack<BinTree> s = new Stack<BinTree>();
43         while (t != null || !s.empty()) {
44             while (t != null) {
45                 System.out.print(t.date);
46                 s.push(t);
47                 t = t.lchild;
48             }
49             if (!s.empty()) {
50                 t = s.pop();
51                 t = t.rchild;
52             }
53         }
54     }
55
56     // 中序遍历非递归
57     public static void InOrder2(BinTree t) {
58         Stack<BinTree> s = new Stack<BinTree>();
59         while (t != null || !s.empty()) {
60             while (t != null) {
61                 s.push(t);
62                 t = t.lchild;
63             }
64             if (!s.empty()) {
65                 t = s.pop();
66                 System.out.print(t.date);
67                 t = t.rchild;
68             }
69         }
70     }
71
72     // 后序遍历非递归
73     public static void PostOrder2(BinTree t) {
74         Stack<BinTree> s = new Stack<BinTree>();
75         Stack<Integer> s2 = new Stack<Integer>();
76         Integer i = new Integer(1);
77         while (t != null || !s.empty()) {
78             while (t != null) {
79                 s.push(t);
80                 s2.push(new Integer(0));
81                 t = t.lchild;
82             }
83             while (!s.empty() && s2.peek().equals(i)) {
84                 s2.pop();
85                 System.out.print(s.pop().date);
86             }
87
88             if (!s.empty()) {
89                 s2.pop();
90                 s2.push(new Integer(1));
91                 t = s.peek();
92                 t = t.rchild;
93             }
94         }
95     }
96