最后一次数据结构作业

group02/812350401/src/main/java/com/github/miniyk2012/coding2017/basic/tree/BinarySearchTree.java

@@ -1,7 +1,6 @@
 package com.github.miniyk2012.coding2017.basic.tree;
 
-import java.util.List;
-import java.util.NoSuchElementException;
+import java.util.*;
 
 public class BinarySearchTree<T extends Comparable> {
 
@@ -113,19 +112,106 @@ private BinaryTreeNode<T> deleteMin(BinaryTreeNode<T> root) {
         return root;
     }
 
+    /**
+     * 树的层序遍历
+     * @return
+     */
     public List<T> levelVisit(){
+        return levelVisit(root);
+    }
 
-        return null;
+    private List<T> levelVisit(BinaryTreeNode<T> root) {
+        ArrayDeque<BinaryTreeNode<T>> queue = new ArrayDeque<>();
+        List<T> list = new LinkedList<>();
+        if (root == null) return list;
+        queue.add(root);
+        BinaryTreeNode<T> head;
+        while (!queue.isEmpty()) {
+            head = queue.remove();
+            if (head.left != null) {
+                queue.add(head.left);
+            }
+            if (head.right != null) {
+                queue.add(head.right);
+            }
+            list.add(head.getData());
+        }
+        return list;
     }
+
+    /**
+     * 判断该二叉树是否是查找二叉树
+     * @return
+     */
     public boolean isValid(){
-        return false;
+        if (root == null) return true;
+        BinarySearchTree<T> leftTree = new BinarySearchTree<>(root.left);
+        BinarySearchTree<T> rightTree = new BinarySearchTree<>(root.right);
+        boolean isValid = true;
+        if (root.left != null) {
+            if (!leftTree.isValid() || root.data.compareTo(leftTree.findMax())<0) {
+                isValid = false;
+            }
+        }
+        if (isValid && root.right != null) {
+            if (!rightTree.isValid() || root.data.compareTo(rightTree.findMin())>0) {
+                isValid = false;
+            }
+        }
+        return isValid;
     }
+
+    /**
+     * 返回n1, n2的最低公共父节点(n1, n2分别为搜索二叉树中某节点的值，只考虑各节点值不同的情况, 且n1, n2是不同的节点值)
+     * @param n1
+     * @param n2
+     * @return
+     */
     public T getLowestCommonAncestor(T n1, T n2){
-        return null;
+        return  getLowestCommonAncestor(root, n1, n2);
+    }
 
+    private T getLowestCommonAncestor(BinaryTreeNode<T> root, T n1, T n2) {
+        if (root == null) {
+            return null;
+        }
+        if (n1.compareTo(root.data)>0 && n2.compareTo(root.data)>0) {
+            return getLowestCommonAncestor(root.right, n1, n2);
+        }
+        if (n1.compareTo(root.data)<0 && n2.compareTo(root.data)<0) {
+            return getLowestCommonAncestor(root.left, n1, n2);
+        }
+        return root.data;
     }
+
+    /**
+     * 返回一个数组，每个元素e满足n1<e<n2（n1, n2为任意值，不一定是某节点的值）
+     * @param n1
+     * @param n2
+     * @return
+     */
     public List<T> getNodesBetween(T n1, T n2){
-        return null;
+        List<T> elements = new ArrayList<>();
+        getNodesBetween(elements, root, n1, n2);
+        return elements;
+    }
+
+    private void getNodesBetween(List<T> elements, BinaryTreeNode<T> root, T n1, T n2) {
+        if (root == null) {
+            return;
+        }
+        // 若根节点在范围内，把根节点加入element
+        if (n1.compareTo(root.data)<0 && n2.compareTo(root.data)>0) {
+            elements.add(root.data);
+        }
+        // 找左子树的满足范围的节点
+        if (n1.compareTo(root.data)<0) {
+            getNodesBetween(elements, root.left, n1, n2);
+        }
+        // 找右子树的满足范围的节点
+        if (n2.compareTo(root.data)>0) {
+            getNodesBetween(elements, root.right, n1, n2);
+        }
     }
 }
 

group02/812350401/src/main/java/com/github/miniyk2012/coding2017/basic/tree/BinarySearchTreeTest.java

@@ -1,28 +1,50 @@
 package com.github.miniyk2012.coding2017.basic.tree;
 
-import static org.junit.Assert.fail;
 
 import org.junit.After;
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 
+import java.util.Arrays;
+import java.util.List;
+import static org.junit.Assert.assertTrue;
 
 
 public class BinarySearchTreeTest {
 
 	BinarySearchTree<Integer> tree = null;
-
+	BinarySearchTree<Integer> tree2 = null;
+	BinarySearchTree<Integer> tree3 = null;
+
 	@Before
 	public void setUp() throws Exception {
+	    /**
+	          6
+             / \
+	        2   8
+           / \
+          1   4
+             /
+            3
+
+         */
 		BinaryTreeNode<Integer> root = new BinaryTreeNode<Integer>(6);
 		root.left = new BinaryTreeNode<Integer>(2);
 		root.right = new BinaryTreeNode<Integer>(8);
 		root.left.left = new BinaryTreeNode<Integer>(1);
 		root.left.right = new BinaryTreeNode<Integer>(4);
 		root.left.right.left = new BinaryTreeNode<Integer>(3);
 		tree = new BinarySearchTree<Integer>(root);
-	}
+
+		BinaryTreeNode<Integer> root2 = new BinaryTreeNode<>(5);
+        tree2 = new BinarySearchTree<>(root2);
+
+        BinaryTreeNode<Integer> root3 = new BinaryTreeNode<>(5);
+        root3.left = new BinaryTreeNode<Integer>(6);
+        tree3 = new BinarySearchTree<>(root3);
+
+    }
 
 	@After
 	public void tearDown() throws Exception {
@@ -76,4 +98,78 @@ public void testRemoveRoot() {
 
 	}
 
+	@Test
+	public void testIsValid() {
+        assertTrue(tree.isValid());
+        assertTrue(tree2.isValid());
+        Assert.assertFalse(tree3.isValid());
+
+        BinarySearchTree<Integer> tree4 = new BinarySearchTree<>(tree.root.left);
+        assertTrue(tree4.isValid());
+
+        tree.root.right.right = new BinaryTreeNode<>(7);
+        Assert.assertFalse(tree.isValid());
+        assertTrue(tree4.isValid());
+
+    }
+
+	@Test
+	public void testLevelVisit() {
+        List<Integer> list = tree.levelVisit();
+        Assert.assertEquals("[6, 2, 8, 1, 4, 3]", Arrays.toString(list.toArray()));
+        List<Integer> list2 = tree2.levelVisit();
+        Assert.assertEquals("[5]", Arrays.toString(list2.toArray()));
+        BinarySearchTree<Integer> nullTree = new BinarySearchTree<Integer>(null);
+        List<Integer> nullList = nullTree.levelVisit();
+        Assert.assertEquals("[]", Arrays.toString(nullList.toArray()));
+    }
+
+    @Test
+    public void testGetLowestCommonAncestor() {
+	    int ancestor = tree.getLowestCommonAncestor(1, 3);
+        Assert.assertEquals(2, ancestor);
+        ancestor = tree.getLowestCommonAncestor(2, 3);
+        Assert.assertEquals(2, ancestor);
+        ancestor = tree.getLowestCommonAncestor(2, 6);
+        Assert.assertEquals(6, ancestor);
+        ancestor = tree.getLowestCommonAncestor(1, 8);
+        Assert.assertEquals(6, ancestor);
+        ancestor = tree.getLowestCommonAncestor(3, 4);
+        Assert.assertEquals(4, ancestor);
+    }
+
+    @Test
+    public void testGetNodesBetween() {
+	    List<Integer> list = tree.getNodesBetween(1, 4);
+	    List <Integer> expectedList = Arrays.asList(2, 3);
+        assertTrue(list.containsAll(expectedList) && expectedList.containsAll(list));
+
+        list = tree.getNodesBetween(6, 8);
+        expectedList = Arrays.asList();
+        assertTrue(list.containsAll(expectedList) && expectedList.containsAll(list));
+
+        list = tree.getNodesBetween(4, 6);
+        expectedList = Arrays.asList();
+        assertTrue(list.containsAll(expectedList) && expectedList.containsAll(list));
+
+        list = tree.getNodesBetween(1, 6);
+        expectedList = Arrays.asList(2, 4, 3);
+        assertTrue(list.containsAll(expectedList) && expectedList.containsAll(list));
+
+        list = tree.getNodesBetween(1, 8);
+        expectedList = Arrays.asList(2, 6, 4, 3);
+        assertTrue(list.containsAll(expectedList) && expectedList.containsAll(list));
+
+
+        // 当n1, n2不一定为某节点值时
+        list = tree.getNodesBetween(5, 8);
+        expectedList = Arrays.asList(6);
+        assertTrue(list.containsAll(expectedList) && expectedList.containsAll(list));
+
+        list = tree.getNodesBetween(-1, 9);
+        expectedList = Arrays.asList(1, 2, 6, 4, 3, 8);
+        assertTrue(list.containsAll(expectedList) && expectedList.containsAll(list));
+
+    }
+
 }