二叉树:

package Tree;import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;public class BinTree {private class TreeNode{int data;TreeNode left;TreeNode right;public TreeNode(){data = 0;left = null;right = null;}public TreeNode(int e){data = e;left = null;right = null;}}private TreeNode binRoot;public BinTree(){binRoot = null;}public TreeNode getRoot(){return binRoot;}public boolean pre_in_orderBuildTree(int[] preOrder,int[] inOrder){int len = preOrder.length;if (len==0) return false;binRoot =  pre_in_orderDfsTree(preOrder,inOrder,0,len-1,0,len-1);return true;}public boolean in_post_orderBuildTree(int[] inOrder,int[] postOrder){int len = inOrder.length;if (len==0) return false;binRoot =  in_post_orderDfsTree(inOrder,postOrder,0,len-1,0,len-1);return true;}private TreeNode pre_in_orderDfsTree(int[] preOrder,int[] inOrder,int l1,int h1,int l2,int h2){if (l1 > h1) return null;int val = preOrder[l1];TreeNode root = new TreeNode(val);if (l1==h1) return root;int mid = 0;while(inOrder[l2+mid]!=val) mid++;root.left = pre_in_orderDfsTree(preOrder,inOrder,l1+1,l1+mid,l2,l2+mid-1);root.right = pre_in_orderDfsTree(preOrder,inOrder,l1+mid+1,h1,l2+mid+1,h2);return root;}private TreeNode in_post_orderDfsTree(int[] inOrder,int[] postOrder,int l1,int h1,int l2,int h2){if (l1 > h1) return null;int val = postOrder[h2];TreeNode root = new TreeNode(val);if (l1==h1) return root;int mid = 0;while(inOrder[l1+mid]!=val) mid++;root.left = in_post_orderDfsTree(inOrder,postOrder,l1,l1+mid-1,l2,l2+mid-1);root.right = in_post_orderDfsTree(inOrder,postOrder,l1+mid+1,h1,l2+mid,h2-1);return root;}public void preOrderTree(){ArrayList<Integer> arrays = new ArrayList<>();preOrderDfsTree(binRoot,arrays);System.out.println(arrays);}private void preOrderDfsTree(TreeNode root, ArrayList<Integer> arrays){if (root!=null){arrays.add(root.data);preOrderDfsTree(root.left,arrays);preOrderDfsTree(root.right,arrays);}}public void inOrderTree(){ArrayList<Integer> arrays = new ArrayList<>();inOrderDfsTree(binRoot,arrays);System.out.println(arrays);}private void inOrderDfsTree(TreeNode root, ArrayList<Integer> arrays){if (root!=null){inOrderDfsTree(root.left,arrays);arrays.add(root.data);inOrderDfsTree(root.right,arrays);}}public void postOrderTree(){ArrayList<Integer> arrays = new ArrayList<>();postOrderDfsTree(binRoot,arrays);System.out.println(arrays);}private void postOrderDfsTree(TreeNode root, ArrayList<Integer> arrays){if (root!=null){postOrderDfsTree(root.left,arrays);postOrderDfsTree(root.right,arrays);arrays.add(root.data);}}public void inOrderTree_Stack(){TreeNode p = binRoot;ArrayList<Integer> arrays = new ArrayList<>();if (p==null){System.out.println(arrays);return ;}Stack<TreeNode> s = new Stack<>();while(p!=null || !s.empty()){while(p!=null){s.add(p);p = p.left;}if (!s.empty()){p = s.pop();arrays.add(p.data);p = p.right;}}System.out.println(arrays);}public void preOrderTree_Stack(){Stack<TreeNode> s = new Stack<>();ArrayList<Integer> arrays = new ArrayList<>();TreeNode p = binRoot;if (p==null){System.out.println(arrays);return ;}while(p!=null || !s.empty()){while(p!=null) {s.add(p);arrays.add(p.data);p = p.left;}if (!s.empty()){p = s.pop();p = p.right;}}System.out.println(arrays);}public void  postOrderTree_Stack(){TreeNode p = binRoot;ArrayList<Integer> arrays = new ArrayList<>();Stack<TreeNode> s = new Stack<>();if (p==null){System.out.println(arrays);return ;}s.add(p);while(!s.empty()){p = s.pop();if (p!=null){s.push(p);s.push(null);if (p.right!=null) s.push(p.right);if (p.left!=null) s.push(p.left);}else{p = s.pop();arrays.add(p.data);}}System.out.println(arrays);}public void levelOrderTree(){Queue<TreeNode> q = new LinkedList<>();ArrayList<Integer> arrays = new ArrayList<>();TreeNode p = binRoot;if(p==null){System.out.println(arrays);return ;}q.add(p);while(!q.isEmpty()){p = q.poll();arrays.add(p.data);if (p.left!=null) q.add(p.left);if (p.right!=null) q.add(p.right);}System.out.println(arrays);}}

测试类:

package Tree;public class TestBinTree {public static void main(String[] args){BinTree bt = new BinTree();int[] pre = {3,9,20,15,7};int[] in = {9,3,15,20,7};int[] post = {9,15,7,20,3};bt.pre_in_orderBuildTree(pre,in);BinTree bt2 = new BinTree();bt2.in_post_orderBuildTree(in,post);bt.preOrderTree();bt.preOrderTree_Stack();bt.inOrderTree();bt.inOrderTree_Stack();bt.postOrderTree();bt.postOrderTree_Stack();bt.levelOrderTree();}
}