java 實現二叉樹深度優先遍歷的 前、中、後序遍歷(遞迴)
阿新 • • 發佈:2019-02-06
import java.util.*; public class BinaryTree { protected Node root; public BinaryTree(Node root) { this.root = root; } public Node getRoot() { return root; } /** 構造樹 */ public static Node init() { Node a = new Node('A'); Node b = new Node('B', null, a); Node c = new Node('C'); Node d = new Node('D', b, c); Node e = new Node('E'); Node f = new Node('F', e, null); Node g = new Node('G', null, f); Node h = new Node('H', d, g); return h;// root } /** 訪問節點 */ public static void visit(Node p) { System.out.print(p.getKey() + " "); } /** 遞迴實現前序遍歷 */ static void preorder(Node p) { if (p != null) { visit(p); preorder(p.getLeft()); preorder(p.getRight()); } } /** 遞迴實現中序遍歷 */ static void inorder(Node p) { if (p != null) { inorder(p.getLeft()); visit(p); inorder(p.getRight()); } } /** 遞迴實現後序遍歷 */ static void postorder(Node p) { if (p != null) { postorder(p.getLeft()); postorder(p.getRight()); visit(p); } } /** 層次遍歷*/ static void levelorder(Node p){ if(p==null) return; Queue< Node> queue=new LinkedList< Node>(); queue.offer(p); while(queue.size()>0){ Node temp=queue.poll(); visit(temp); if(temp.getLeft()!=null){ queue.offer(temp.getLeft()); } if(temp.getRight()!=null){ queue.offer(temp.getRight()); } } } // 求二叉樹的高度 static int height(Node tree) { if (tree == null) return 0; else { int leftTreeHeight = height(tree.getLeft()); int rightTreeHeight = height(tree.getRight());; return leftTreeHeight > rightTreeHeight ? leftTreeHeight + 1: rightTreeHeight + 1; } } // 求二叉樹的結點總數 static int nodes(Node tree) { if (tree == null) return 0; else { int left = nodes(tree.getLeft()); int right = nodes(tree.getRight()); return left + right + 1; } } // 求二叉樹葉子節點的總數 static int leaf(Node tree) { if (tree == null) return 0; else { int left = leaf(tree.getLeft()); int right = leaf(tree.getRight()); if (tree.getLeft() == null && tree.getRight() == null) return left + right + 1; else return left + right; } } //將二叉樹所有結點的左右子樹交換 static void swapTree(Node root){ if(root != null) { Node tmp = root.getLeft(); root.setLeft(root.getRight()); root.setRight(tmp); swapTree(root.getLeft()); swapTree(root.getRight()); } } /** * getLeafNodes: 遞迴求解給定二叉樹的所有葉子結點 * @param root 給定二叉樹的根結點 * @param leaflist 給定二叉樹的所有葉子結點 */ static void getLeafNodes(Node root, List< Node> leaflist) { if (root != null) { if (root.getLeft() == null && root.getRight() == null) { leaflist.add(root); return ; } getLeafNodes(root.getLeft(), leaflist); getLeafNodes(root.getRight(), leaflist); } } /** * longestPath: 遞迴求解給定二叉樹的一條最長路徑 如果有多條,輸出其中一條 * @param root 給定二叉樹的根結點 * @param longestPath 存放二叉樹的最長路徑上的結點 */ static void longestPath(Node root, List< Node> longestPath) { if (root != null) { longestPath.add(root); if (root.getLeft() == null && root.getRight() == null) { // 左右子樹均空 return ; } List< Node> leftLongestPath = new ArrayList< Node>(); List< Node> rightLongestPath = new ArrayList< Node>(); longestPath(root.getLeft(), leftLongestPath); longestPath(root.getRight(), rightLongestPath); if (leftLongestPath.size() >= rightLongestPath.size()) { longestPath.addAll(leftLongestPath); } else if (leftLongestPath.size() < rightLongestPath.size()) { longestPath.addAll(rightLongestPath); } } } /** * @param args */ public static void main(String[] args) { BinaryTree tree = new BinaryTree(init()); System.out.print(" 前序遍歷:"); preorder(tree.getRoot()); System.out.println(); System.out.print(" 中序遍歷:"); inorder(tree.getRoot()); System.out.println(); System.out.print(" 後序遍歷:"); postorder(tree.getRoot()); System.out.println(); System.out.println(); System.out.println("層次遍歷"); levelorder(tree.getRoot()); System.out.println(); System.out.println(); System.out.println("葉子結點數"); System.out.println(leaf(tree.getRoot())); System.out.println("總結點數"); System.out.println(nodes(tree.getRoot())); System.out.println("樹的高度"); System.out.println(height(tree.getRoot())); } } public class Node { private char key; private Node left, right; public Node(char key) { this(key, null, null); } public Node(char key, Node left, Node right) { this.key = key; this.left = left; this.right = right; } public char getKey() { return key; } public void setKey(char key) { this.key = key; } public Node getLeft() { return left; } public void setLeft(Node left) { this.left = left; } public Node getRight() { return right; } public void setRight(Node right) { this.right = right; } }