problem 18

Author: yangrubing

swordForOffer/src/main/java/problem06/ContructBinaryTree.java

@@ -1,10 +1,10 @@
 package problem06;
 
+import utils.BinaryTreeNode;
+
 import java.security.InvalidParameterException;
 import java.util.Arrays;
 
-import utils.BinaryTreeNode;
-
 /**
  * 输入前序和中序遍历结果，重建二叉树
  * @author bjyangrubing
@@ -44,8 +44,7 @@ public static void preOrder(BinaryTreeNode root)
 	{
 		if (root != null)
 		{
-			if (root.value != null)
-				System.out.println(root.value);
+			System.out.println(root.value);
 			preOrder(root.leftNode);
 			preOrder(root.rightNode);
 		}
@@ -61,8 +60,7 @@ public static void inOrder(BinaryTreeNode root)
 		if (root != null)
 		{
 			inOrder(root.leftNode);
-			if (root.value != null)
-				System.out.println(root.value);
+			System.out.println(root.value);
 			inOrder(root.rightNode);
 		}
 

swordForOffer/src/main/java/problem15/FindKthToTail.java

@@ -10,32 +10,37 @@
  * 3. 如果输入的k大于链表的长度，则返回null
  * Created by yrb on 2016/8/16.
  */
-public class FindKthToTail {
+public class FindKthToTail
+{
 
-    public ListNode findKthToTail(ListNode head, int k) {
-        if (k <= 0 || head == null) {
-            return null;
-        }
+	public ListNode findKthToTail(ListNode head, int k)
+	{
+		if (k <= 0 || head == null)
+		{
+			return null;
+		}
 
-        //设置两个指针，一个快，一个慢
-        ListNode aHead = head;
-        ListNode behind = null;
-        //快的先走k-1步
-        for (int i = 0; i < k - 1; i++) {
-            if (aHead.next != null)
-                aHead = aHead.next;
-            else
-                return null;//如果k大于链表的长度，则直接返回null
-        }
-        //这时慢的指向第一个节点
-        behind = head;
-        //快的和慢的一起走，当快的走到末尾的时候，慢的指向的就是倒数第K个
-        while (aHead.next != null) {
+		//设置两个指针，一个快，一个慢
+		ListNode aHead = head;
+		ListNode behind = null;
+		//快的先走k-1步
+		for (int i = 0; i < k - 1; i++)
+		{
+			if (aHead.next != null)
+				aHead = aHead.next;
+			else
+				return null;//如果k大于链表的长度，则直接返回null
+		}
+		//这时慢的指向第一个节点
+		behind = head;
+		//快的和慢的一起走，当快的走到末尾的时候，慢的指向的就是倒数第K个
+		while (aHead.next != null)
+		{
 
-            aHead = aHead.next;
-            behind = behind.next;
-        }
-        return behind;
-    }
+			aHead = aHead.next;
+			behind = behind.next;
+		}
+		return behind;
+	}
 
 }

swordForOffer/src/main/java/problem16/ReverseList.java

@@ -6,22 +6,25 @@
  * 反转链表
  * Created by yrb on 2016/8/16.
  */
-public class ReverseList {
+public class ReverseList
+{
 
-    public ListNode reverseList(ListNode pHead) {
-        ListNode pReverseHead = null;//反转后的头
-        ListNode pNode = pHead;//当前节点
-        ListNode pPrev = null;//当前节点的前一个节点
+	public ListNode reverseList(ListNode pHead)
+	{
+		ListNode pReverseHead = null;//反转后的头
+		ListNode pNode = pHead;//当前节点
+		ListNode pPrev = null;//当前节点的前一个节点
 
-        while (pNode != null) {
-            ListNode pNext = pNode.next;
-            if (pNext == null)
-                pReverseHead = pNode;
-            pNode.next = pPrev;
-            pPrev = pNode;
-            pNode = pNext;
-        }
-        return pReverseHead;
-    }
+		while (pNode != null)
+		{
+			ListNode pNext = pNode.next;
+			if (pNext == null)
+				pReverseHead = pNode;
+			pNode.next = pPrev;
+			pPrev = pNode;
+			pNode = pNext;
+		}
+		return pReverseHead;
+	}
 
 }

swordForOffer/src/main/java/problem17/MergeSortedLists.java

@@ -0,0 +1,36 @@
+package problem17;
+
+import utils.ListNode;
+
+/**合并两个排序的列表
+ * 合并两个链表并使新链表中的节点仍然是递增排序的
+ * Created by bjyangrubing on 2016/8/17.
+ */
+public class MergeSortedLists
+{
+
+	public ListNode merge(ListNode head1, ListNode head2)
+	{
+
+		//递归的基准情况
+		if (head1 == null)
+			return head2;
+		else if (head2 == null)
+			return head1;
+
+		ListNode mHead = null;
+		//如果head1的值<head2的值，则将合并后的头设置为head1
+		if (head1.value < head2.value)
+		{
+			mHead = head1;
+			mHead.next = merge(head1.next, head2);//递归合并剩余链表
+		}
+		else
+		{
+			mHead = head2;
+			mHead.next = merge(head1, head2.next);
+		}
+		return mHead;
+	}
+
+}

swordForOffer/src/main/java/problem17/MergeSortedLists.png

@@ -0,0 +1,72 @@
+package problem18;
+
+import utils.BinaryTreeNode;
+
+/**
+ * 树的子结构，判断
+ * Created by bjyangrubing on 2016/8/17.
+ */
+public class SubstructureInTree
+{
+
+	public boolean hasSubTree(BinaryTreeNode treeA, BinaryTreeNode treeB)
+	{
+		if (treeB == null)//首先判断如果，如果B为空树，返回true
+			return true;
+		if (treeA == null)//如果B不为null，A为null返回false
+			return false;
+
+		boolean result = false;
+
+		if (treeA != null && treeB != null)
+		{
+			if (treeA.value == treeB.value)
+				result = doesTreeAHasTreeB(treeA, treeB);//判断以当前节点为根节点的数是不是和treeB相同
+			if (!result)
+				result = hasSubTree(treeA.leftNode, treeB) || hasSubTree(treeA.rightNode, treeB);
+		}
+		return result;
+	}
+
+	private boolean doesTreeAHasTreeB(BinaryTreeNode treeA, BinaryTreeNode treeB)
+	{
+		if (treeB == null)//首先判断如果，如果B为空树，返回true
+			return true;
+		if (treeA == null)//如果B不为null，A为null返回false
+			return false;
+		if (treeA.value != treeB.value)//如果两个节点的值不相同，则直接返回false
+			return false;
+		//递归判断treeA和treeB的节点是否相同
+		return doesTreeAHasTreeB(treeA.leftNode, treeB.leftNode) && doesTreeAHasTreeB(treeA.rightNode, treeB.rightNode);
+	}
+
+	public static void main(String[] args)
+	{
+		BinaryTreeNode rootA = new BinaryTreeNode(8);
+		BinaryTreeNode a_node1 = new BinaryTreeNode(8);
+		BinaryTreeNode a_node2 = new BinaryTreeNode(7);
+		BinaryTreeNode a_node3 = new BinaryTreeNode(9);
+		BinaryTreeNode a_node4 = new BinaryTreeNode(2);
+		BinaryTreeNode a_node5 = new BinaryTreeNode(4);
+		BinaryTreeNode a_node6 = new BinaryTreeNode(7);
+		rootA.leftNode = a_node1;
+		rootA.rightNode = a_node2;
+
+		a_node1.leftNode = a_node3;
+		a_node1.rightNode = a_node4;
+
+		a_node4.leftNode = a_node5;
+		a_node4.rightNode = a_node6;
+
+		BinaryTreeNode rootB = new BinaryTreeNode(8);
+		BinaryTreeNode b_node1 = new BinaryTreeNode(9);
+		BinaryTreeNode b_node2 = new BinaryTreeNode(2);
+
+		rootB.leftNode = b_node1;
+		rootB.rightNode = b_node2;
+
+		SubstructureInTree substructureInTree = new SubstructureInTree();
+		boolean result = substructureInTree.hasSubTree(rootA, rootB);
+		System.out.println(result);
+	}
+}

swordForOffer/src/main/java/problem18/SubstructureInTree.java

@@ -2,7 +2,16 @@
 
 public class BinaryTreeNode
 {
-	public Integer value;
+	public int value;
+
+	public BinaryTreeNode()
+	{
+	}
+
+	public BinaryTreeNode(int value)
+	{
+		this.value = value;
+	}
 
 	public BinaryTreeNode leftNode;
 

swordForOffer/src/main/java/utils/BinaryTreeNode.java

@@ -7,32 +7,34 @@
 /**
  * Created by yrb on 2016/8/16.
  */
-public class FindKthToTailTest {
-    @Test
-    public void test() {
-        ListNode six = new ListNode();
-        ListNode one = new ListNode();
-        ListNode two = new ListNode();
-        ListNode three = new ListNode();
-        ListNode four = new ListNode();
-        ListNode five = new ListNode();
-        one.value = 1;
-        two.value = 2;
-        three.value = 3;
-        four.value = 4;
-        five.value = 5;
-        six.value = 6;
-        one.next = two;
-        two.next = three;
-        three.next = four;
-        four.next = five;
-        five.next = six;
-        Assert.assertEquals(3, new FindKthToTail().findKthToTail(one, 4).value);
+public class FindKthToTailTest
+{
+	@Test
+	public void test()
+	{
+		ListNode six = new ListNode();
+		ListNode one = new ListNode();
+		ListNode two = new ListNode();
+		ListNode three = new ListNode();
+		ListNode four = new ListNode();
+		ListNode five = new ListNode();
+		one.value = 1;
+		two.value = 2;
+		three.value = 3;
+		four.value = 4;
+		five.value = 5;
+		six.value = 6;
+		one.next = two;
+		two.next = three;
+		three.next = four;
+		four.next = five;
+		five.next = six;
+		Assert.assertEquals(3, new FindKthToTail().findKthToTail(one, 4).value);
 
-        Assert.assertEquals(null, new FindKthToTail().findKthToTail(one, 0));
+		Assert.assertEquals(null, new FindKthToTail().findKthToTail(one, 0));
 
-        Assert.assertEquals(null, new FindKthToTail().findKthToTail(one, 8));
+		Assert.assertEquals(null, new FindKthToTail().findKthToTail(one, 8));
 
-        Assert.assertEquals(null, new FindKthToTail().findKthToTail(null, 1));
-    }
+		Assert.assertEquals(null, new FindKthToTail().findKthToTail(null, 1));
+	}
 }

swordForOffer/src/test/java/problem15/FindKthToTailTest.java

@@ -7,31 +7,33 @@
 /**
  * Created by yrb on 2016/8/16.
  */
-public class ReverseListTest {
-    @Test
-    public void test() {
-        ListNode six = new ListNode();
-        ListNode one = new ListNode();
-        ListNode two = new ListNode();
-        ListNode three = new ListNode();
-        ListNode four = new ListNode();
-        ListNode five = new ListNode();
-        one.value = 1;
-        two.value = 2;
-        three.value = 3;
-        four.value = 4;
-        five.value = 5;
-        six.value = 6;
-        one.next = two;
-        two.next = three;
-        three.next = four;
-        four.next = five;
-        five.next = six;
-        new ReverseList().reverseList(one);
+public class ReverseListTest
+{
+	@Test
+	public void test()
+	{
+		ListNode six = new ListNode();
+		ListNode one = new ListNode();
+		ListNode two = new ListNode();
+		ListNode three = new ListNode();
+		ListNode four = new ListNode();
+		ListNode five = new ListNode();
+		one.value = 1;
+		two.value = 2;
+		three.value = 3;
+		four.value = 4;
+		five.value = 5;
+		six.value = 6;
+		one.next = two;
+		two.next = three;
+		three.next = four;
+		four.next = five;
+		five.next = six;
+		new ReverseList().reverseList(one);
 
-        Assert.assertEquals(1, two.next.value);
+		Assert.assertEquals(1, two.next.value);
 
-        Assert.assertEquals(5, six.next.value);
+		Assert.assertEquals(5, six.next.value);
 
-    }
+	}
 }