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mJackiemJackie
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20190110
1 parent 7ccd186 commit 09371df

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5 files changed

+159
-17
lines changed

‎code/lc10.java

+1-1
Original file line numberDiff line numberDiff line change
@@ -32,7 +32,7 @@ public static boolean isMatch(String s, String p) {
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}else{
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dp[i][j] = (dp[i-1][j] || dp[i-1][j-1] || dp[i][j-2]);
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//dp[i-1][j] * 表示前面字符出现多次
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//dp[i-1][j-1] * 表示前面字符出现一次
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//dp[i-1][j-1] * 表示前面字符出现一次 dp[i]dp[j-1]也行
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// dp[i][j-2] *表示前边字符出现0次，覆盖这些情况. s="ba" p="baa*"; s="a" p="ab*a*"
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}
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}

‎code/lc236.java

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@@ -0,0 +1,58 @@
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package code;
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import java.util.*;
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/*
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* 236. Lowest Common Ancestor of a Binary Tree
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* 题意：二叉树上两个节点的公共祖先
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* 难度：Medium
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* 分类：Tree
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* 思路：递归，迭代两种方法
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* Tips：注意递归时怎么返回。很经典的题目。
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*/
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public class lc236 {
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public class TreeNode {
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int val;
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TreeNode left;
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TreeNode right;
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TreeNode(int x) { val = x; }
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}
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public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {//递归
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if( root==null || root==p || root==q )
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return root;
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TreeNode left = lowestCommonAncestor(root.left, p, q);
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TreeNode right = lowestCommonAncestor(root.right, p, q);
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if( left!=null && right!=null ) //回溯返回。哪边不为空，返回哪边，否则返回自己。
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return root;
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else if(left!=null)
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return left;
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else return right;
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}
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public TreeNode lowestCommonAncestor2(TreeNode root, TreeNode p, TreeNode q) {
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Map<TreeNode, TreeNode> parent = new HashMap<>(); //用map存储节点的父亲节点，便于查找
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Stack<TreeNode> stack = new Stack<>();
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parent.put(root, null);
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stack.push(root);
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while (!parent.containsKey(p) || !parent.containsKey(q)) {
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TreeNode node = stack.pop();
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if (node.left != null) {
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parent.put(node.left, node);
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stack.push(node.left);
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}
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if (node.right != null) {
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parent.put(node.right, node);
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stack.push(node.right);
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}
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}
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Set<TreeNode> ancestors = new HashSet<>();
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while (p != null) {
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ancestors.add(p);
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p = parent.get(p);
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}
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while (!ancestors.contains(q))
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q = parent.get(q);
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return q;
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}
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}

‎code/lc238.java

+25
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@@ -0,0 +1,25 @@
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package code;
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/*
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* 238. Product of Array Except Self
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* 题意：数组中除了nums[i]的乘积
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* 难度：Medium
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* 分类：Array
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* 思路：左右两个方向简单dp，空间压缩以后可以直接迭代的方法算
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* Tips：
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*/
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public class lc238 {
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public int[] productExceptSelf(int[] nums) {
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int[] res = new int[nums.length];
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res[0] = 1;
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for (int i = 1; i < nums.length; i++) {
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res[i] = res[i-1]*nums[i-1];
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}
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int temp = 1; //用temp记录右边值，每次迭代一下
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res[nums.length-1] = res[nums.length-1] * temp;
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for (int i = nums.length-2; i>=0 ; i--) {
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temp = temp * nums[i+1];
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res[i] = res[i] * temp;
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}
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return res;
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}
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}

‎code/lc297.java

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package code;
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import java.util.Arrays;
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import java.util.Deque;
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import java.util.LinkedList;
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/*
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* 297. Serialize and Deserialize Binary Tree
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* 题意：序列化，反序列化树
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* 难度：Hard
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* 分类：Tree, Design
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* 思路：
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* Tips：
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*/
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public class lc297 {
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public class TreeNode {
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int val;
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TreeNode left;
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TreeNode right;
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TreeNode(int x) { val = x; }
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}
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public class Codec {
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private static final String spliter = ",";
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private static final String NN = "X";
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// Encodes a tree to a single string.
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public String serialize(TreeNode root) {
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StringBuilder sb = new StringBuilder();
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buildString(root, sb);
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return sb.toString();
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}
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private void buildString(TreeNode node, StringBuilder sb) {
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if (node == null) {
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sb.append(NN).append(spliter);
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} else {
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sb.append(node.val).append(spliter);
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buildString(node.left, sb);
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buildString(node.right,sb);
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}
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}
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// Decodes your encoded data to tree.
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public TreeNode deserialize(String data) {
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Deque<String> nodes = new LinkedList<>();
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nodes.addAll(Arrays.asList(data.split(spliter)));
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return buildTree(nodes);
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}
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private TreeNode buildTree(Deque<String> nodes) {
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String val = nodes.remove();
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if (val.equals(NN)) return null;
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else {
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TreeNode node = new TreeNode(Integer.valueOf(val));
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node.left = buildTree(nodes);
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node.right = buildTree(nodes);
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return node;
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}
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}
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}
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}

‎readme.md

+15-16
Original file line numberDiff line numberDiff line change
@@ -79,26 +79,25 @@ Welcome to improve this project with me.*
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| 148 | [Sort List](https://leetcode.com/problems/sort-list/) |Medium| [Java](./code/lc148.java)
8080
| 152 | [Maximum Product Subarray](https://leetcode.com/problems/maximum-product-subarray/) |Medium| [Java](./code/lc152.java)
8181
| 155 | [Min Stack](https://leetcode.com/problems/min-stack/) | Easy | [Java](./code/lc155.java)
82-
| 160 | [Intersection of Two Linked Lists](https://leetcode.com/problems/intersection-of-two-linked-lists/) | Easy | [Java]
83-
| 169 | [Majority Element](https://leetcode.com/problems/majority-element/) | Easy | [Java]
84-
| 198 | [House Robber](https://leetcode.com/problems/house-robber/) | Easy | [Java]
85-
| 200 | [Number of Islands](https://leetcode.com/problems/number-of-islands/) |Medium| [Java]
86-
| 206 | [Reverse Linked List](https://leetcode.com/problems/reverse-linked-list/) | Easy |[Java]
87-
| 207 | [Course Schedule](https://leetcode.com/problems/course-schedule/) |Medium|[Java]
88-
| 208 | [Implement Trie (Prefix Tree)](https://leetcode.com/problems/implement-trie-prefix-tree/) |Medium| [Java]
89-
| 215 | [Kth Largest Element in an Array](https://leetcode.com/problems/kth-largest-element-in-an-array/) |Medium| [Java]
90-
| 218 | [Subarray Sum Equals K](https://leetcode.com/problems/subarray-sum-equals-k) | Hard |[Java]
91-
| 221 | [Maximal Square](https://leetcode.com/problems/maximal-square/) |Medium| [Java]
92-
| 226 | [Invert Binary Tree](https://leetcode.com/problems/invert-binary-tree/) | Easy | [Java]
93-
| 234 | [Palindrome Linked List](https://leetcode.com/problems/palindrome-linked-list/) | Easy | [Java]
94-
| 236 | [Lowest Common Ancestor of a Binary Tree](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/) |Medium| [Java]
95-
| 238 | [Product of Array Except Self](https://leetcode.com/problems/product-of-array-except-self/) |Medium| [Java]
96-
| 239 | [Sliding Window Maximum](https://leetcode.com/problems/sliding-window-maximum/) | Hard | [Java] |
82+
| 160 | [Intersection of Two Linked Lists](https://leetcode.com/problems/intersection-of-two-linked-lists/) | Easy | [Java](./code/lc160.java)
83+
| 169 | [Majority Element](https://leetcode.com/problems/majority-element/) | Easy | [Java](./code/lc169.java)
84+
| 198 | [House Robber](https://leetcode.com/problems/house-robber/) | Easy | [Java](./code/lc198.java)
85+
| 200 | [Number of Islands](https://leetcode.com/problems/number-of-islands/) |Medium| [Java](./code/lc200.java)
86+
| 206 | [Reverse Linked List](https://leetcode.com/problems/reverse-linked-list/) | Easy |[Java](./code/lc206.java)
87+
| 207 | [Course Schedule](https://leetcode.com/problems/course-schedule/) |Medium|[Java](./code/lc207.java)
88+
| 208 | [Implement Trie (Prefix Tree)](https://leetcode.com/problems/implement-trie-prefix-tree/) |Medium| [Java](./code/lc208.java)
89+
| 215 | [Kth Largest Element in an Array](https://leetcode.com/problems/kth-largest-element-in-an-array/) |Medium| [Java](./code/lc215.java)
90+
| 221 | [Maximal Square](https://leetcode.com/problems/maximal-square/) |Medium| [Java](./code/lc221.java)
91+
| 226 | [Invert Binary Tree](https://leetcode.com/problems/invert-binary-tree/) | Easy | [Java](./code/lc226.java)
92+
| 234 | [Palindrome Linked List](https://leetcode.com/problems/palindrome-linked-list/) | Easy | [Java](./code/lc234.java)
93+
| 236 | [Lowest Common Ancestor of a Binary Tree](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/) |Medium| [Java](./code/lc236.java)
94+
| 238 | [Product of Array Except Self](https://leetcode.com/problems/product-of-array-except-self/) |Medium| [Java](./code/lc238.java)
95+
| 239 | [Sliding Window Maximum](https://leetcode.com/problems/sliding-window-maximum/) | Hard | [Java](./code/lc239.java)
9796
| 240 | [Search a 2D Matrix II](https://leetcode.com/problems/search-a-2d-matrix-ii/) |Medium| [Java]
9897
| 279 | [Perfect Squares](https://leetcode.com/problems/perfect-squares/) |Medium| [Java]
9998
| 283 | [Move Zeroes](https://leetcode.com/problems/move-zeroes/)| Easy | [Java]
10099
| 287 | [Find the Duplicate Number](https://leetcode.com/problems/find-the-duplicate-number/) | Hard | [Java]
101-
| 297 | [Serialize and Deserialize Binary Tree](https://leetcode.com/problems/serialize-and-deserialize-binary-tree/) | Hard | [Java]
100+
| 297 | [Serialize and Deserialize Binary Tree](https://leetcode.com/problems/serialize-and-deserialize-binary-tree/) | Hard | [Java](./code/lc297.java)
102101
| 300 | [Longest Increasing Subsequence](https://leetcode.com/problems/longest-increasing-subsequence/) |Medium| [Java]
103102
| 309 | [Best Time to Buy and Sell Stock with Cooldown](https://leetcode.com/problems/best-time-to-buy-and-sell-stock-with-cooldown/) |Medium| [Java]
104103
| 312 | [Burst Balloons](https://leetcode.com/problems/burst-balloons/) | Hard | [Java]

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