diff --git a/AlgorithmHomework3.md b/AlgorithmHomework3.md index 968fcf1..7dbb320 100755 --- a/AlgorithmHomework3.md +++ b/AlgorithmHomework3.md @@ -21,7 +21,7 @@ Leetcode: 35,58,83 - **Leetcode提交结果：** - ![image-20200313210334196](https://raw.githubusercontent.com/SunnyQjm/picgo_0/master/img/image-20200313210334196.png) + ![image-20200313210334196](AlgorithmHomework3.assets/image-20200313210334196.png) - **代码：** @@ -56,7 +56,7 @@ Leetcode: 35,58,83 - **Leetcode提交结果：** - ![image-20200313211905775](https://raw.githubusercontent.com/SunnyQjm/picgo_0/master/img/image-20200313213736914.png) + ![image-20200313211905775](AlgorithmHomework3.assets/image-20200313213736914.png) - **代码：** @@ -89,12 +89,13 @@ Leetcode: 35,58,83 - **算法思路：** - 用一个set记录当前遍历过的值 - - 遍历到每一个节点，用set检查当前值是否存在于set，如果存在则删除该节点 - - - **Leetcode提交结果：** - - ![image-20200313213736914](https://raw.githubusercontent.com/SunnyQjm/picgo_0/master/img/image-20200313211905775.png) - + +- 遍历到每一个节点，用set检查当前值是否存在于set，如果存在则删除该节点 + +- **Leetcode提交结果：** + + ![image-20200313213736914](AlgorithmHomework3.assets/image-20200313211905775.png) + - **代码：** ```python diff --git a/AlgorithmHomework8.assets/image-20200416230344311.png b/AlgorithmHomework8.assets/image-20200416230344311.png new file mode 100644 index 0000000..48fb6ef Binary files /dev/null and b/AlgorithmHomework8.assets/image-20200416230344311.png differ diff --git a/AlgorithmHomework8.assets/image-20200423115932875.png b/AlgorithmHomework8.assets/image-20200423115932875.png new file mode 100644 index 0000000..6175dbd Binary files /dev/null and b/AlgorithmHomework8.assets/image-20200423115932875.png differ diff --git a/AlgorithmHomework8.assets/image-20200423211525664.png b/AlgorithmHomework8.assets/image-20200423211525664.png new file mode 100644 index 0000000..3a72a0b Binary files /dev/null and b/AlgorithmHomework8.assets/image-20200423211525664.png differ diff --git a/AlgorithmHomework8.assets/image-20200423221735514.png b/AlgorithmHomework8.assets/image-20200423221735514.png new file mode 100644 index 0000000..2be1963 Binary files /dev/null and b/AlgorithmHomework8.assets/image-20200423221735514.png differ diff --git a/AlgorithmHomework8.assets/微信图片_20200416172437.jpg b/AlgorithmHomework8.assets/微信图片_20200416172437.jpg new file mode 100644 index 0000000..1777129 Binary files /dev/null and b/AlgorithmHomework8.assets/微信图片_20200416172437.jpg differ diff --git a/AlgorithmHomework8.md b/AlgorithmHomework8.md new file mode 100644 index 0000000..8682067 --- /dev/null +++ b/AlgorithmHomework8.md @@ -0,0 +1,146 @@ +# Algorithm Homework 8 + +> 姓名：阙建明 +> +> 学号：1901213139 + +## 作业要求： + +Leetcode: 72, 312, 729 + +## 题解： + +- ### Leetcode problem 72 + + > [编辑距离](https://leetcode-cn.com/problems/edit-distance/) + + - **算法思路：** + 1. `dp[i][j] `表示word1的前i个字母和word2的前j个字母的编辑距离 + 2. 在word1中删除一个字符，等价于在word2中适当位置添加一个字符 + 3. 如果`word1[i - 1]` == `word2[j - 1]`: + - `dp[i - 1][j]`的基础上在word1上增加一个字符 => 操作+1 + - `dp[i][j - 1]`的基础上在word2上增加一个字符 => 操作+1 + - `dp[i - 1][j - 1]`的基础上不做操作 => 操作+0 + 3. 如果word1[i - 1] != word2[j - 1] + - `dp[i - 1][j]`的基础上在word1上增加一个字符 => 操作+1 + - `dp[i][j - 1]`的基础上在word2上增加一个字符 => 操作+1 + - `dp[i - 1][j - 1]`的基础上修改`word1[i]`，使得`word1[i] = word2[j]` => 操作+1 + + - **Leetcode提交结果：** + + ![image-20200423115932875](AlgorithmHomework8.assets/image-20200423115932875.png) + + - **代码：** + + ```python + class Solution(object): + def minDistance(self, word1, word2): + """ + :type word1: str + :type word2: str + :rtype: int + """ + n, m = len(word1), len(word2) + if n * m == 0: + return n + m + dp = [[0] * (m + 1) for _ in range(n + 1)] + for i in range(n + 1): + dp[i][0] = i + for j in range(m + 1): + dp[0][j] = j + + for i in range(1, n + 1): + for j in range(1, m + 1): + tmp1 = dp[i - 1][j] + 1 + tmp2 = dp[i][j - 1] + 1 + tmp3 = dp[i - 1][j - 1] + if word1[i - 1] != word2[j - 1]: + tmp3 += 1 + dp[i][j] = min(tmp1, tmp2, tmp3) + return dp[-1][-1] + ``` + +- ### Leetcode problem 312 + + > [ 戳气球](https://leetcode-cn.com/problems/burst-balloons/) + + - **算法思路：** + + - 采用动态规划的思想，`dp[left][right]` 表示戳破开区间（left, right）中的气球所能得到的最大金币数量； + + - 为了处理边缘的数据，这边在初始数组的左右两边各加一个值为1的元素； + + - 考虑从没有气球开始把气球逐个加入，则添加第i个气球后能得到的最大金币数为： + + $nums[left] * nums[i] * nums[right] + dp(left, i) + dp(i, right)$ + +- **Leetcode提交结果：** + + ![image-20200423211525664](AlgorithmHomework8.assets/image-20200423211525664.png) + + - **代码：** + + ```python + class Solution(object): + def maxCoins(self, nums): + """ + :type nums: List[int] + :rtype: int + """ + nums = [1] + nums + [1] + n = len(nums) + dp = [[0] * n for _ in range(n)] + for left in range(n-2, -1, -1): + for right in range(left+2, n): + dp[left][right] = max(nums[left] * nums[i] * nums[right] + dp[left][i] + dp[i][right] for i in range(left+1, right)) + return dp[0][n-1] + ``` + +- ### Leetcode problem 729 + + > [我的日程安排表 I](https://leetcode-cn.com/problems/my-calendar-i/) + + - **算法思路：** + + - 每次判断现有的行程中有没有和当前要添加的行程有重叠的部分； + - 如果有重叠，则直接返回Fase + - 如果没有重叠，则将新的行程插入到特定位置，保证行程数组是按序插入的 + + - **Leetcode提交结果：** + + ![image-20200423221735514](AlgorithmHomework8.assets/image-20200423221735514.png) + + - **代码：** + + ```python + class MyCalendar(object): + + def __init__(self): + self.calendar = [] + + def book(self, start, end): + """ + :type start: int + :type end: int + :rtype: bool + """ + + if len(self.calendar) == 0: + self.calendar.append([start, end]) + return True + + for i in range(len(self.calendar)): + if self.calendar[i][0] >= end: + if i == 0: + self.calendar.insert(0, [start, end]) + return True + elif self.calendar[i - 1][1] <= start: + self.calendar.insert(i, [start, end]) + return True + if self.calendar[-1][1] <= start: + self.calendar.append([start, end]) + return True + return False + ``` + + \ No newline at end of file