第一周作业#38

ABOUTME.md

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+# 关于我
+
+【关于自己】：大家好，我是刘剑波，坐标江苏省南通市崇川区，性格内向，希望在算法训练营与优秀的大家一起学习，也希望培养起刻意练习的习惯，持续学习。
+【关于工作】：目前从事Java开发工作，主要负责公司网站群产品的功能升级和大数据产品的落地。
+【工作之外】：平时骑车上班，每天大约20公里，有时候看看书，有时候看看电影，喜欢纪录频道。
+【想跟你分享】：如果给我10分钟，我希望跟同学们分享关于我职业发展中的一些思考。

Week_01/id_38/LeetCode_15_038.java

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+import java.util.*;
+
+/*
+ * @lc app=leetcode.cn id=15 lang=java
+ *
+ * [15] 三数之和
+ * 要点1:答案中不包含重复的三元组
+ */
+class LeetCode_15_038 {
+    public List<List<Integer>> threeSum(int[] nums) {
+        if (nums.length < 3) return null;
+        Arrays.sort(nums);
+
+        List<List<Integer>> result = new ArrayList<>();
+
+        if (nums[0] <= 0 && nums[nums.length - 1] >= 0) {
+            for (int i = 0; i < nums.length - 2; ++i) {
+                if (i > 0 && nums[i-1] == nums[i]) continue;
+
+                int l = i +1, r = nums.length - 1;
+                while(l < r){
+                    if(nums[r] > -nums[i]-nums[l]){
+                        while(l < r && nums[r-1] == nums[r]) r--;
+                        r--;
+                    }
+                    else if(nums[r] < -nums[i]-nums[l]){
+                        while(l < r && nums[l+1] == nums[l]) l++;
+                        l++;
+                    }
+                    else{
+                        result.add(Arrays.asList(nums[i],nums[l],nums[r]));
+                        while(l < r && nums[r-1] == nums[r]) r--;
+                        while(l < r && nums[l+1] == nums[l]) l++;
+                        r--;
+                        l++;
+                    }
+                }
+            }
+        } 
+
+        return result;
+    }
+
+    public static void main(String[] args) {
+        LeetCode_15_038 testCode_15_038 = new LeetCode_15_038();
+        int[] nums = new int[]{-1,0,1,2,-1,-4};
+        System.out.println(testCode_15_038.threeSum(nums));
+    }
+}
+

Week_01/id_38/LeetCode_242_038.java

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+/*
+ * @lc app=leetcode.cn id=242 lang=java
+ *
+ * [242] 有效的字母异位词
+ * 要点1:答案中不包含重复的三元组
+ */
+class LeetCode_242_038 {
+
+    public boolean isAnagram(String s, String t) {
+        if (s.length() != t.length()) return false;
+
+        int[] hash = new int[26];
+        for(int i = 0; i < s.length(); ++i) {
+            hash[s.charAt(i) - 'a']++;
+            hash[t.charAt(i) - 'a']--;
+        }
+
+        for (int i = 0; i < hash.length; ++i) {
+            if (hash[i] != 0) return false;
+        }
+
+        return true;
+    }
+
+    public static void main(String[] args) {
+        LeetCode_242_038 testCode_242_038 = new LeetCode_242_038();
+        System.out.println(testCode_242_038.isAnagram("aaab", "baaa"));
+    }
+}
+

Week_01/id_38/LeetCode_26_038.java

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+/*
+ * @lc app=leetcode.cn id=26 lang=java
+ *
+ * [26] 删除排序数组中的重复项
+ * 要点1:有序数组
+ * 要点2:原地删除
+ */
+class LeetCode_26_038 {
+
+    /**
+     * 时间复杂度：O(n)
+     * 空间复杂度：不需要额外空间
+     * @param nums
+     * @return
+     */
+    public int removeDuplicates(int[] nums) {
+        // check valid
+        if (nums.length == 0) return 0;
+
+        // process
+        int i = 0;
+        for (int j = 1; j < nums.length; ++j){
+            if (nums[i] != nums[j]) {
+                i++;
+                nums[i] = nums[j];
+            }
+        }
+        return i + 1;
+    }
+
+    public static void main(String[] args) {
+        LeetCode_26_038 testCode_26_038 = new LeetCode_26_038();
+        int[] nums = new int[]{1, 1, 2, 2, 4, 5, 7};
+        System.out.println(testCode_26_038.removeDuplicates(nums));
+    }
+}
+

Week_01/id_38/LeetCode_50_038.java

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+/*
+ * @lc app=leetcode.cn id=50 lang=java
+ *
+ * [50] Pow(x, n)
+ */
+class LeetCode_50_038 {
+    public double myPow(double x, int n) {
+        if (n == 0) return 1.0;
+
+        double half = myPow(x, n / 2);
+        if (n % 2 == 0) {
+            return half * half;
+        } else {
+            return half * half * x;
+        }
+
+    }
+
+    public static void main(String[] args) {
+        LeetCode_50_038 testCode_50_038 = new LeetCode_50_038();
+        System.out.println(testCode_50_038.myPow(2, 10));
+    }
+}
+

Week_01/id_38/README.md

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+# 学习笔记
+
+## 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/)
+
+<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>[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>[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/)
+
+[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/)
+
+[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/)
+
+[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/)
+
+[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/)
+
+
+---
+
+### 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/)
+
+[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/)
+
+[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/)
+
+[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/)
+