二叉树的递归,非递归遍历(java)

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  1 import java.util.Stack;  2 import java.util.HashMap;  3   4 public class BinTree {  5     private char date;  6     private BinTree lchild;  7     private BinTree rchild;  8   9     public BinTree(char c) { 10         date = c; 11     } 12  13     // 先序遍历递归 14     public static void preOrder(BinTree t) { 15         if (t == null) { 16             return; 17         } 18         System.out.print(t.date); 19         preOrder(t.lchild); 20         preOrder(t.rchild); 21     } 22  23     // 中序遍历递归 24     public static void InOrder(BinTree t) { 25         if (t == null) { 26             return; 27         } 28         InOrder(t.lchild); 29         System.out.print(t.date); 30         InOrder(t.rchild); 31     } 32  33     // 后序遍历递归 34     public static void PostOrder(BinTree t) { 35         if (t == null) { 36             return; 37         } 38         PostOrder(t.lchild); 39         PostOrder(t.rchild); 40         System.out.print(t.date); 41     } 42  43     // 先序遍历非递归 44     public static void preOrder2(BinTree t) { 45         Stack<BinTree> s = new Stack<BinTree>(); 46         while (t != null || !s.empty()) { 47             while (t != null) { 48                 System.out.print(t.date); 49                 s.push(t); 50                 t = t.lchild; 51             } 52             if (!s.empty()) { 53                 t = s.pop(); 54                 t = t.rchild; 55             } 56         } 57     } 58  59     // 中序遍历非递归 60     public static void InOrder2(BinTree t) { 61         Stack<BinTree> s = new Stack<BinTree>(); 62         while (t != null || !s.empty()) { 63             while (t != null) { 64                 s.push(t); 65                 t = t.lchild; 66             } 67             if (!s.empty()) { 68                 t = s.pop(); 69                 System.out.print(t.date); 70                 t = t.rchild; 71             } 72         } 73     } 74  75     // 后序遍历非递归 76     public static void PostOrder2(BinTree t) { 77         Stack<BinTree> s = new Stack<BinTree>(); 78         Stack<Integer> s2 = new Stack<Integer>(); 79         Integer i = new Integer(1); 80         while (t != null || !s.empty()) { 81             while (t != null) { 82                 s.push(t); 83                 s2.push(new Integer(0)); 84                 t = t.lchild; 85             } 86             while (!s.empty() && s2.peek().equals(i)) { 87                 s2.pop(); 88                 System.out.print(s.pop().date); 89             } 90  91             if (!s.empty()) { 92                 s2.pop(); 93                 s2.push(new Integer(1)); 94                 t = s.peek(); 95                 t = t.rchild; 96             } 97         } 98     } 99 100     public static void main(String[] args) {101         BinTree b1 = new BinTree('a');102         BinTree b2 = new BinTree('b');103         BinTree b3 = new BinTree('c');104         BinTree b4 = new BinTree('d');105         BinTree b5 = new BinTree('e');106 107         /**108          *      a 109          *     / /110          *    b   c111          *   / /112          *  d   e113          */114         b1.lchild = b2;115         b1.rchild = b3;116         b2.lchild = b4;117         b2.rchild = b5;118 119         BinTree.preOrder(b1);120         System.out.println();121         BinTree.preOrder2(b1);122         System.out.println();123         BinTree.InOrder(b1);124         System.out.println();125         BinTree.InOrder2(b1);126         System.out.println();127         BinTree.PostOrder(b1);128         System.out.println();129         BinTree.PostOrder2(b1);130     }131 }
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