Java实现二叉树的多种遍历

简述：

用Java实现二叉树的前序，中序，后序，层序遍历, S型层序遍历

算法简述：

前三个算法在于输出当前节点的位置，

1 前序： 在递归左右儿子之前，输出当前节点

[java] view plain copy

  1. void PreOrderPrint(){  
  2.     System.out.print(value.toString() + " ");  
  3. if(left != null)  
  4.         left.PreOrderPrint();  
  5. if(right != null)  
  6.         right.PreOrderPrint();  
  7. } 

2 中序：在递归左右儿子中间，输出

[java] view plain copy

  1. void InOrderPrint(){  
  2. if(left != null)  
  3.         left.InOrderPrint();  
  4.     System.out.print(value.toString() + " ");  
  5. if(right != null)  
  6.         right.InOrderPrint();  
  7. } 

后序：在递归左右儿子之后输出

[java] view plain copy

  1. void PostOrderPrint(){  
  2. if(left != null)  
  3.         left.PostOrderPrint();  
  4. if(right != null)  
  5.         right.PostOrderPrint();  
  6.     System.out.print(value.toString() + " ");  
  7. } 

3 层序遍历，这里的实现方式类似于两个簸箕（queue1 和 queue2)之间互相倒，知道谁都没有后继节点位置，即两个簸箕都为空，此处是两个队列都为空

[java] view plain copy

  1. void LevelOrderPrint(){  
  2. if(this == null)  
  3. throw new IllegalArgumentException("null node !");  
  4.     Queue<Node<E>> queue1 = new LinkedList<Node<E>>();  
  5.     Queue<Node<E>> queue2 = new LinkedList<Node<E>>();  
  6.     queue1.add(this);  
  7. while(!queue1.isEmpty() || !queue2.isEmpty()){  
  8. if(queue2.isEmpty()){  
  9. while(!queue1.isEmpty()){  
  10.                 Node<E> currentNode = queue1.poll();  
  11.                 System.out.print(currentNode.value.toString() + " ");  
  12. if(currentNode.left != null){  
  13.                     queue2.add(currentNode.left);  
  14.                 }  
  15. if(currentNode.right != null){  
  16.                     queue2.add(currentNode.right);  
  17.                 }  
  18.             }  
  19.         }  
  20. else{  
  21. while(!queue2.isEmpty()){  
  22.                 Node<E> currentNode = queue2.poll();  
  23.                 System.out.print(currentNode.value.toString() + " ");  
  24. if(currentNode.left != null){  
  25.                     queue1.add(currentNode.left);  
  26.                 }  
  27. if(currentNode.right != null){  
  28.                     queue1.add(currentNode.right);  
  29.                 }  
  30.             }  
  31.         }  
  32.         System.out.println();  
  33.     }  
  34. } 

4  S型层序遍历，就是把上面使用的queue换为stack，注意左右子节点添加顺序，就可以了

[java] view plain copy

  1. //Print By Level S-style
  2. public void S_LevelOrderPrint(){  
  3.     Stack<Node<E>> stack1 = new Stack<Node<E>>();  
  4.     Stack<Node<E>> stack2 = new Stack<Node<E>>();  
  5.     stack1.add(this);  
  6. while(!stack1.isEmpty() || !stack2.isEmpty()){  
  7. if(stack1.isEmpty()){  
  8. while(!stack2.isEmpty()){  
  9.                 Node<E> currentNode = stack2.pop();  
  10.                 System.out.print(currentNode.value + " ");  
  11. if(currentNode.left != null)  
  12.                     stack1.push(currentNode.left);  
  13. if(currentNode.right != null)  
  14.                     stack1.push(currentNode.right);  
  15.             }  
  16.         }else{  
  17. while(!stack1.isEmpty()){  
  18.                 Node<E> currentNode = stack1.pop();  
  19.                 System.out.print(currentNode.value + " ");  
  20. if(currentNode.right != null)  
  21.                     stack2.add(currentNode.right);  
  22. if(currentNode.left != null)  
  23.                     stack2.add(currentNode.left);  
  24.             }  
  25.         }  
  26.         System.out.println();  
  27.     }  
  28. } 

下面是主要代码，包括测试代码

代码：

[java] view plain copy

  1. package offer;  
  2. import java.util.LinkedList;  
  3. import java.util.Queue;  
  4. import java.util.Stack;  
  5. class Node<E extends Comparable<E>>{  
  6.     Node<E> left;  
  7.     Node<E> right;  
  8.     E value;  
  9.     Node(){  
  10.         left = null;  
  11.         right = null;  
  12.         value = null;  
  13.     }  
  14.     Node(E value){  
  15. this.value = value;  
  16.         left = null;  
  17.         right = null;  
  18.     }  
  19. void PreOrderPrint(){  
  20.         System.out.print(value.toString() + " ");  
  21. if(left != null)  
  22.             left.PreOrderPrint();  
  23. if(right != null)  
  24.             right.PreOrderPrint();  
  25.     }  
  26. void InOrderPrint(){  
  27. if(left != null)  
  28.             left.InOrderPrint();  
  29.         System.out.print(value.toString() + " ");  
  30. if(right != null)  
  31.             right.InOrderPrint();  
  32.     }  
  33. void PostOrderPrint(){  
  34. if(left != null)  
  35.             left.PostOrderPrint();  
  36. if(right != null)  
  37.             right.PostOrderPrint();  
  38.         System.out.print(value.toString() + " ");  
  39.     }  
  40. //Print By Level
  41. void LevelOrderPrint(){  
  42. if(this == null)  
  43. throw new IllegalArgumentException("null node !");  
  44.         Queue<Node<E>> queue1 = new LinkedList<Node<E>>();  
  45.         Queue<Node<E>> queue2 = new LinkedList<Node<E>>();  
  46.         queue1.add(this);  
  47. while(!queue1.isEmpty() || !queue2.isEmpty()){  
  48. if(queue2.isEmpty()){  
  49. while(!queue1.isEmpty()){  
  50.                     Node<E> currentNode = queue1.poll();  
  51.                     System.out.print(currentNode.value.toString() + " ");  
  52. if(currentNode.left != null){  
  53.                         queue2.add(currentNode.left);  
  54.                     }  
  55. if(currentNode.right != null){  
  56.                         queue2.add(currentNode.right);  
  57.                     }  
  58.                 }  
  59.             }  
  60. else{  
  61. while(!queue2.isEmpty()){  
  62.                     Node<E> currentNode = queue2.poll();  
  63.                     System.out.print(currentNode.value.toString() + " ");  
  64. if(currentNode.left != null){  
  65.                         queue1.add(currentNode.left);  
  66.                     }  
  67. if(currentNode.right != null){  
  68.                         queue1.add(currentNode.right);  
  69.                     }  
  70.                 }  
  71.             }  
  72.             System.out.println();  
  73.         }  
  74.     }  
  75. //Print By Level S-style
  76. public void S_LevelOrderPrint(){  
  77.         Stack<Node<E>> stack1 = new Stack<Node<E>>();  
  78.         Stack<Node<E>> stack2 = new Stack<Node<E>>();  
  79.         stack1.add(this);  
  80. while(!stack1.isEmpty() || !stack2.isEmpty()){  
  81. if(stack1.isEmpty()){  
  82. while(!stack2.isEmpty()){  
  83.                     Node<E> currentNode = stack2.pop();  
  84.                     System.out.print(currentNode.value + " ");  
  85. if(currentNode.left != null)  
  86.                         stack1.push(currentNode.left);  
  87. if(currentNode.right != null)  
  88.                         stack1.push(currentNode.right);  
  89.                 }  
  90.             }else{  
  91. while(!stack1.isEmpty()){  
  92.                     Node<E> currentNode = stack1.pop();  
  93.                     System.out.print(currentNode.value + " ");  
  94. if(currentNode.right != null)  
  95.                         stack2.add(currentNode.right);  
  96. if(currentNode.left != null)  
  97.                         stack2.add(currentNode.left);  
  98.                 }  
  99.             }  
  100.             System.out.println();  
  101.         }  
  102.     }  
  103. }  
  104. class BinarySearchTree<E extends Comparable<E>>{  
  105. private Node<E> root;  
  106. public Node<E> getRoot(){  
  107. return root;  
  108.     }  
  109.     BinarySearchTree(){  
  110.         root = null;  
  111.     }  
  112. public void InsertNode(E value){  
  113. if(root == null){  
  114.             root = new Node<E>(value);  
  115. return;  
  116.         }  
  117.         Node<E> currentNode = root;  
  118. while(true){  
  119. if(value.compareTo(currentNode.value) > 0){  
  120. if(currentNode.right == null){  
  121.                     currentNode.right = new Node<E>(value);  
  122. break;  
  123.                 }  
  124.                 currentNode = currentNode.right;  
  125.             }else{  
  126. if(currentNode.left == null){  
  127.                     currentNode.left = new Node<E>(value);  
  128. break;  
  129.                 }  
  130.                 currentNode = currentNode.left;  
  131.             }  
  132.         }  
  133.     }  
  134. }  
  135. public class LevelPrintOfBinaryTree<E extends Comparable<E>> {  
  136. public static void main(String[] args) {  
  137.         BinarySearchTree<Integer> tree = new BinarySearchTree<Integer>();  
  138.         {  
  139.             tree.InsertNode(4);  
  140.             tree.InsertNode(2);  
  141.             tree.InsertNode(1);  
  142.             tree.InsertNode(3);  
  143.             tree.InsertNode(6);  
  144.             tree.InsertNode(5);  
  145.             tree.InsertNode(7);  
  146.             tree.InsertNode(8);  
  147.         }  
  148.         System.out.print("PreOrderPrint: ");  
  149.         tree.getRoot().PreOrderPrint();  
  150.         System.out.print("\nInOrderPrint: ");  
  151.         tree.getRoot().InOrderPrint();  
  152.         System.out.print("\nPostOrderPrint: ");  
  153.         tree.getRoot().PostOrderPrint();  
  154.         System.out.println("\nLevelOrderPrint: ");  
  155.         tree.getRoot().LevelOrderPrint();  
  156.         System.out.println("\nS_LevelOrderPrint: ");  
  157.         tree.getRoot().S_LevelOrderPrint();  
  158.     }  
  159. } 

 

输入测试的树：

1a852537-474a-4738-a37e-5d07400baf67

输出：

93616a00-167a-4379-b985-c61b90844089

来源： http://blog.csdn.net/anialy/article/details/8145114

posted on 2016-03-15 14:22  执念saying  阅读(154)  评论(0)  编辑  收藏  举报

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