Tree Traversal (preOrder, inOrder, postOrder, levelOrder, zigzagOrder) 

  1 class TreeNode{
  2     char data;
  3     TreeNode left;
  4     TreeNode right;
  5     static int leaf;
  6     static boolean flag=true;
  7     TreeNode (char c){
  8         data = c;
  9     }
 10     TreeNode (TreeNode n){
 11         data = n.data;
 12         left = n.left;
 13         right = n.right;
 14     }
 15     
 16     public static void visit(TreeNode n){
 17         if(n == null)
 18             System.out.print("");
 19         else{
 20             if(flag){
 21                 System.out.print(n.data);
 22                 flag = false;
 23             }else{
 24                 System.out.print(" " + n.data);
 25             }
 26         }
 27         if(n.left == null && n.right == null) {
 28             leaf++;
 29         }
 30     }
 31     
 32     public static void preOrder(TreeNode root){
 33         if(root == null) return;
 34         visit(root);
 35         preOrder(root.left);
 36         preOrder(root.right);
 37     }
 38     
 39 //    public static void preOrder2(TreeNode root){
 40 //        if(root == null) return;
 41 //        Stack<TreeNode> stack = new Stack<TreeNode>();
 42 //        stack.add(root);
 43 //        while(!stack.isEmpty()){
 44 //            TreeNode top = stack.pop();
 45 //            visit(top);
 46 //            if(top.right != null) stack.add(top.right);
 47 //            if(top.left != null) stack.add(top.left);
 48 //        }
 49 //    }
 50     
 51     public static void preOrder2(TreeNode root){
 52         if(root == null) return;
 53         Stack<TreeNode> stack = new Stack<TreeNode>();
 54         while(!stack.isEmpty() || root != null){
 55             if(root != null){
 56                 stack.push(root);
 57                 visit(root);
 58                 root = root.left;
 59             }else{
 60                 root = stack.pop();
 61                 root = root.right;
 62             }    
 63         }
 64     }
 65     public static void inOrder(TreeNode root){
 66         if(root == null) return;
 67         inOrder(root.left);
 68         visit(root);
 69         inOrder(root.right);
 70     }
 71     
 72     public static void inOrder2(TreeNode root){
 73         if(root == null) return;
 74         Stack<TreeNode> stack = new Stack<TreeNode>();
 75         while(!stack.empty() || root != null){
 76             if(root != null){
 77                 stack.push(root);
 78                 root = root.left;
 79             }else{
 80                 //reached leftMost
 81                 root = stack.pop();
 82                 visit(root);
 83                 root = root.right;
 84             }
 85         }
 86     }
 87     
 88     public static void postOrder(TreeNode root){
 89         if(root == null) return;
 90         postOrder(root.left);
 91         postOrder(root.right);
 92         visit(root);
 93     }
 94     
 95     public static void levelOrder(TreeNode root){
 96         if(root == null) return;
 97         LinkedList<TreeNode> q = new LinkedList<TreeNode>();
 98         q.add(root);
 99         while(!q.isEmpty()){
100             TreeNode head = q.removeFirst();
101             visit(head);
102             if(head.left != null) q.add(head.left);
103             if(head.right != null) q.add(head.right);
104         }
105     }
106     
107     public static void zigzagOrder(TreeNode root){
108         LinkedList<TreeNode> currentLevel = new LinkedList<TreeNode>();
109         int level = 0;
110         if(root != null) 
111             currentLevel.add(root);
112         while(!currentLevel.isEmpty()){
113             LinkedList<TreeNode> nextLevel = new LinkedList<TreeNode>();
114             ArrayList<TreeNode> list = new ArrayList<TreeNode>();
115             for(TreeNode node : currentLevel){
116                 list.add(node);
117                 if(node.left != null)
118                     nextLevel.add(node.left);
119                 if(node.right != null)
120                     nextLevel.add(node.right);
121             }
122             if(level%2 == 1)
123                 Collections.reverse(list);
124             for(int i = 0; i < list.size(); i++)
125                 visit(list.get(i));
126             currentLevel = nextLevel;
127             level++;
128         }
129         
130     }
131     
132 }

 

posted @ 2013-01-30 02:38  cradle  阅读(873)  评论(0)    收藏  举报