第三周作业#38

Week_01/id_38/LeetCode_104_038.java

@@ -0,0 +1,40 @@
+/*
+ * @lc app=leetcode.cn id=104 lang=java
+ *
+ * [104] 二叉树的最大深度
+ */
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class LeetCode_104_038 {
+    public int maxDepth(TreeNode root) {
+        if (root == null) {
+          return 0;
+        } else {
+          int left_height = maxDepth(root.left);
+          int right_height = maxDepth(root.right);
+          return java.lang.Math.max(left_height, right_height) + 1;
+        }
+    }
+
+    public static void main(String[] args) {
+        LeetCode_104_038 testCode_104_038 = new LeetCode_104_038();
+        System.out.println(testCode_104_038.maxDepth(nums));
+    }
+}
+
+public class TreeNode {
+    int val;
+    TreeNode left;
+    TreeNode right;
+
+    TreeNode(int x) {
+      val = x;
+    }
+  }

Week_01/id_38/README.md

@@ -3,63 +3,62 @@
 ## 第一周题目
 ---
 ### 数组、链表
-<font color="green">【简单】</font>[26. 删除排序数组中的重复项 ](https://leetcode-cn.com/problems/remove-duplicates-from-sorted-array/)
+* [x] <font color="green">【简单】</font>[26. 删除排序数组中的重复项 ](https://leetcode-cn.com/problems/remove-duplicates-from-sorted-array/)
 
-<font color=green>【简单】</font>[189. 旋转数组](https://leetcode-cn.com/problems/rotate-array/)
+* [ ] <font color=green>【简单】</font>[189. 旋转数组](https://leetcode-cn.com/problems/rotate-array/)
 
-<font color=green>【简单】</font>[21. 合并两个有序链表](https://leetcode-cn.com/problems/merge-two-sorted-lists/)
+* [ ] <font color=green>【简单】</font>[21. 合并两个有序链表](https://leetcode-cn.com/problems/merge-two-sorted-lists/)
 
-<font color=green>【简单】</font>[88. 合并两个有序数组](https://leetcode-cn.com/problems/merge-sorted-array/)
+* [ ] <font color=green>【简单】</font>[88. 合并两个有序数组](https://leetcode-cn.com/problems/merge-sorted-array/)
 
-<font color=orange>【中等】</font>[24. 两两交换链表中的节点](https://leetcode-cn.com/problems/swap-nodes-in-pairs/)
+* [ ] <font color=orange>【中等】</font>[24. 两两交换链表中的节点](https://leetcode-cn.com/problems/swap-nodes-in-pairs/)
 
-<font color=orange>【中等】</font>[15. 三数之和](https://leetcode-cn.com/problems/3sum/)
+* [x] <font color=orange>【中等】</font>[15. 三数之和](https://leetcode-cn.com/problems/3sum/)
 
 ---
 
 ### Map & Set
-[242. 有效的字母异位词<font color=green>【简单】</font>](https://leetcode-cn.com/problems/valid-anagram/)
+* [x] [242. 有效的字母异位词<font color=green>【简单】</font>](https://leetcode-cn.com/problems/valid-anagram/)
 
-[49. 字母异位词分组<font color=orange>【中等】</font>](https://leetcode-cn.com/problems/group-anagrams/)
+* [ ] [49. 字母异位词分组<font color=orange>【中等】</font>](https://leetcode-cn.com/problems/group-anagrams/)
 
 ---
 
 ### 堆栈、队列
 
-[1047. 删除字符串中的所有相邻重复项<font color=green>【简单】</font>](https://leetcode-cn.com/problems/remove-all-adjacent-duplicates-in-string/)
+* [ ] [1047. 删除字符串中的所有相邻重复项<font color=green>【简单】</font>](https://leetcode-cn.com/problems/remove-all-adjacent-duplicates-in-string/)
 
-[1021. 删除最外层的括号<font color=green>【简单】</font>](https://leetcode-cn.com/problems/remove-outermost-parentheses/)
+* [ ] [1021. 删除最外层的括号<font color=green>【简单】</font>](https://leetcode-cn.com/problems/remove-outermost-parentheses/)
 
-[84. 柱状图中最大的矩形<font color=red>【困难】</font>](https://leetcode.com/problems/largest-rectangle-in-histogram/)
+* [ ] [84. 柱状图中最大的矩形<font color=red>【困难】</font>](https://leetcode.com/problems/largest-rectangle-in-histogram/)
 
-[42. 接雨水<font color=red>【困难】</font>](https://leetcode.com/problems/trapping-rain-water/)
+* [ ] [42. 接雨水<font color=red>【困难】</font>](https://leetcode.com/problems/trapping-rain-water/)
 
 ---
 
 ### 二分查找
 
-[441. 排列硬币<font color=green>【简单】</font>](https://leetcode-cn.com/problems/arranging-coins/)
+* [ ] [441. 排列硬币<font color=green>【简单】</font>](https://leetcode-cn.com/problems/arranging-coins/)
 
-[50. Pow(x, n)<font color=orange>【中等】</font>](https://leetcode-cn.com/problems/powx-n/)
+* [x] [50. Pow(x, n)<font color=orange>【中等】</font>](https://leetcode-cn.com/problems/powx-n/)
 
-[174. 地下城游戏<font color=red>【困难】</font>](https://leetcode-cn.com/problems/dungeon-game/)
+* [ ] [174. 地下城游戏<font color=red>【困难】</font>](https://leetcode-cn.com/problems/dungeon-game/)
 
 
 ---
 
 ### 递归
 
-[104. 二叉树的最大深度<font color=green>【简单】</font>](https://leetcode-cn.com/problems/maximum-depth-of-binary-tree/)
+* [ ] [104. 二叉树的最大深度<font color=green>【简单】</font>](https://leetcode-cn.com/problems/maximum-depth-of-binary-tree/)
 
-[101. 对称二叉树<font color=green>【简单】</font>](https://leetcode-cn.com/problems/symmetric-tree/)
+* [ ] [101. 对称二叉树<font color=green>【简单】</font>](https://leetcode-cn.com/problems/symmetric-tree/)
 
-[111. 二叉树的最小深度<font color=green>【简单】</font>](https://leetcode-cn.com/problems/minimum-depth-of-binary-tree/)
+* [ ] [111. 二叉树的最小深度<font color=green>【简单】</font>](https://leetcode-cn.com/problems/minimum-depth-of-binary-tree/)
 
-[783. 二叉搜索树结点最小距离<font color=green>【简单】</font>](https://leetcode-cn.com/problems/minimum-distance-between-bst-nodes/)
+* [ ] [783. 二叉搜索树结点最小距离<font color=green>【简单】</font>](https://leetcode-cn.com/problems/minimum-distance-between-bst-nodes/)
 
-[257. 二叉树的所有路径<font color=green>【简单】</font>](https://leetcode-cn.com/problems/binary-tree-paths/)
+* [ ] [257. 二叉树的所有路径<font color=green>【简单】</font>](https://leetcode-cn.com/problems/binary-tree-paths/)
 
-[938. 二叉搜索树的范围和<font color=green>【简单】</font>](https://leetcode-cn.com/problems/range-sum-of-bst/)
-
-[236. 二叉树的最近公共祖先<font color=orange>【中等】</font>](https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-tree/)
+* [ ] [938. 二叉搜索树的范围和<font color=green>【简单】</font>](https://leetcode-cn.com/problems/range-sum-of-bst/)
 
+* [ ] [236. 二叉树的最近公共祖先<font color=orange>【中等】</font>](https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-tree/)

Week_02/id_38/LeetCode_01_038.java

@@ -0,0 +1,66 @@
+import java.util.*;
+
+/*
+ * @lc app=leetcode.cn id=1 lang=java
+ *
+ * [1] 两数之和
+ */
+class LeetCode_01_038 {
+    public int[] twoSum(int[] nums, int target) {
+        // hashmap, 时间 O(n),空间 O(n)
+        Map<Integer, Integer> numDic = new HashMap<Integer, Integer>();
+        // push and process
+        for (int i = 0; i < nums.length; ++i) {
+            if (numDic.containsKey(target - nums[i]) 
+                && numDic.get(target - nums[i]) != i) {
+                return new int[]{numDic.get(target - nums[i]), i};
+            }
+            numDic.put(nums[i], i);
+        }
+
+        throw new IllegalArgumentException("No two sum solution");
+    }
+
+    public int[] twoSum1(int[] nums, int target) {
+        // hashmap, 时间 O(2n),空间 O(n)
+        Map<Integer, Integer> numDic = new HashMap<Integer, Integer>();
+        // push
+        for (int i = 0; i < nums.length; ++i) {
+            numDic.put(nums[i], i);
+        }
+
+        for (int i = 0; i < nums.length; ++i) {
+            if (numDic.containsKey(target - nums[i]) 
+                && numDic.get(target - nums[i]) != i) {
+                return new int[]{i, numDic.get(target - nums[i])};
+            }
+        }
+
+        throw new IllegalArgumentException("No two sum solution");
+    }
+
+    public int[] twoSum2(int[] nums, int target) {
+        // check valid
+
+        // 暴力，时间 O(n^2)，空间 O(1)
+        for (int i = 0; i < nums.length - 1; ++i) {
+            for (int j = i + 1; j < nums.length; ++j) {
+                if (nums[i] + nums[j] == target) {
+                    return new int[]{i, j};
+                }
+            }
+        }
+
+        throw new IllegalArgumentException("No two sum solution");
+    }
+
+    public static void main(String[] args) {
+        LeetCode_01_038 testCode_01_038 = new LeetCode_01_038();
+        int[] nums = new int[]{-1};
+        int[] result = testCode_01_038.twoSum2(nums, 3);
+        for (int i = 0; i < result.length; ++i) {
+            System.out.print(result[i] + ",");
+        }
+    }
+}
+

Week_02/id_38/LeetCode_111_038.java

@@ -0,0 +1,26 @@
+import java.util.*;
+
+/*
+ * @lc app=leetcode.cn id=111 lang=java
+ *
+ * [111] 二叉树的最小深度
+ */
+class LeetCode_111_038 {
+    public int minDepth(TreeNode root) {
+        if (root == null) return 0;
+        if ((root.l == null) && (root.r == null)) return 1;
+        if (root.l == null) return minDepth(root.r) + 1;
+        if (root.r == null) return minDepth(root.l) + 1;
+        return Math.min(minDepth(root.l), minDepth(root.r)) + 1;
+    }
+}
+
+class TreeNode {
+    int val;
+    TreeNode l;
+    TreeNode r;
+    TreeNode(int x) {
+        this.val = x;
+    }
+}
+

Week_02/id_38/LeetCode_242_038.java

@@ -0,0 +1,81 @@
+import java.util.Arrays;
+import java.util.List;
+
+/*
+ * @lc app=leetcode.cn id=242 lang=java
+ *
+ * [242] 有效的字母异位词
+ */
+class LeetCode_242_038 {
+
+    /**
+     * hash
+     * 执行用时：11ms，内存消耗：38.2mb
+     * 时间：O(n), 空间：O(1),n为字符串长度
+     * @param s
+     * @param t
+     * @return
+     */
+    public boolean isAnagram(String s, String t) {
+        // check valid
+        if (equals(s, t)) return true;
+        if (length(s) != length(t)) return false;
+
+        int[] charArr = new int[26];
+        for (int i = 0; i < s.length(); ++i) {
+            charArr[s.charAt(i) - 'a']++;
+            charArr[t.charAt(i) - 'a']--;
+        }
+
+        for (int i : charArr) {
+            if (i != 0) return false;
+        }
+        return true;
+    }
+
+    /**
+     * 将两string排序，然后判断是否相同
+     * 执行用时：317ms，内存消耗：58.2mb
+     * -。-
+     * 自行实现的算法效率正是低，代码也一大坨
+     * @param s
+     * @param t
+     * @return
+     */
+    public boolean isAnagram2(String s, String t) {
+        if (equals(s, t)) return true;
+        if (length(s) != length(t)) return false;
+
+        return equals(stringSort(s), stringSort(t));
+    }
+
+    public String stringSort(String s) {
+        if (isEmpty(s)) return s;
+        String[] sa = s.split("");
+        Arrays.sort(sa);
+        System.out.println(String.join("", sa));
+        return String.join("", sa);
+    }
+
+    public boolean isEmpty(String s) {
+        if (s == null || s.length() == 0) return true;
+        return false;
+    }
+
+    public boolean equals(String s, String t) {
+        if (isEmpty(s) && isEmpty(t)) return true;
+        if (!isEmpty(s) && s.equals(t)) return true;
+        return false;
+    }
+
+    public int length(String s) {
+        if (isEmpty(s)) return 0;
+        return s.length();
+    }
+
+    public static void main(String[] args) {
+        LeetCode_242_038 testCode_242_038 = new LeetCode_242_038();
+        System.out.print(testCode_242_038.isAnagram("ab", "ba"));
+    }
+}
+

Week_02/id_38/README.md

@@ -0,0 +1,48 @@
+# 学习笔记
+
+## 第二周题目
+---
+### 哈希表
+* [x] <font color="green">【简单】</font>[1. 两数之和 ](https://leetcode-cn.com/problems/two-sum/)
+
+* [ ] <font color=green>【简单】</font>[242. 有效的字母异位词](https://leetcode-cn.com/problems/valid-anagram/)
+
+* [ ] <font color=orange>【中等】</font>[3. 无重复字符的最长子串](https://leetcode-cn.com/problems/longest-substring-without-repeating-characters)
+
+* [ ] <font color=orange>【中等】</font>[692. 前K个高频单词](https://leetcode-cn.com/problems/top-k-frequent-words)
+
+* [ ] <font color=red>【困难】</font>[726. 原子的数量](https://leetcode-cn.com/problems/number-of-atoms/)
+
+---
+
+### 二叉树
+* [ ] [111. 二叉树的最小深度<font color=green>【简单】</font>](https://leetcode-cn.com/problems/minimum-depth-of-binary-tree/)
+
+* [ ] [236. 二叉树的最近公共祖先<font color=orange>【中等】</font>](https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-tree/)
+
+* [ ] [101. 对称二叉树<font color=green>【简单】</font>](https://leetcode-cn.com/problems/symmetric-tree/)
+
+* [ ] [103. 二叉树的锯齿形层次遍历<font color=orange>【中等】</font>](https://leetcode-cn.com/problems/binary-tree-zigzag-level-order-traversal/)
+
+* [ ] [102. 二叉树的层次遍历<font color=orange>【中等】</font>](https://leetcode-cn.com/problems/binary-tree-level-order-traversal/)
+
+* [ ] [297. 二叉树的序列化与反序列化<font color=red>【困难】</font>](https://leetcode-cn.com/problems/serialize-and-deserialize-binary-tree/)
+
+
+---
+
+### 二叉搜索树
+* [ ] [783. 二叉搜索树结点最小距离<font color=green>【简单】</font>](https://leetcode-cn.com/problems/minimum-distance-between-bst-nodes/)
+
+* [ ] [235. 二叉搜索树的最近公共祖先<font color=green>【简单】</font>](https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-search-tree/)
+
+* [ ] [98. 验证二叉搜索树<font color=orange>【中等】</font>](https://leetcode-cn.com/problems/validate-binary-search-tree/)
+
+* [ ] [938. 二叉搜索树的范围和<font color=orange>【中等】</font>](https://leetcode-cn.com/problems/range-sum-of-bst/)
+
+* [ ] [220. 存在重复元素 III<font color=orange>【中等】</font>](https://leetcode-cn.com/problems/contains-duplicate-iii/)
+
+* [ ] [315. 计算右侧小于当前元素的个数<font color=red>【困难】</font>](https://leetcode-cn.com/problems/count-of-smaller-numbers-after-self/)
+
+
+---

Week_03/id_38/LeetCode_104_038.java

@@ -0,0 +1,29 @@
+/*
+ * @lc app=leetcode.cn id=104 lang=java
+ *
+ * [104] 二叉树的最大深度
+ */
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class LeetCode_104_038 {
+    public int maxDepth(TreeNode root) {
+      return root == null ? 0 : Math.max(maxDepth(root.left), maxDepth(root.right)) + 1;
+    }
+}
+
+public class TreeNode {
+    int val;
+    TreeNode left;
+    TreeNode right;
+
+    TreeNode(int x) {
+      val = x;
+    }
+  }