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‎Problemset/1048-Longest String Chain/README.md

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# 1048. Longest String Chain
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You are given an array of `words` where each word consists of lowercase English letters.
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<code>word<sub>A</sub></code> is a **predecessor** of <code>word<sub>B</sub></code> if and only if we can insert **exactly one** letter anywhere in <code>word<sub>A</sub></code> **without changing the order of the other characters** to make it equal to <code>word<sub>B</sub></code>.
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* For example, `"abc"` is a **predecessor** of `"abac"`, while `"cba"` is not a **predecessor** of `"bcad"`.
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A **word chain** is a sequence of words <code>[word<sub>1</sub>, word<sub>2</sub>, ..., word<sub>k</sub>]</code> with `k >= 1`, where <code>word<sub>1</sub></code> is a **predecessor** of <code>word<sub>2</sub></code>, <code>word<sub>2</sub></code> is a **predecessor** of <code>word<sub>3</sub></code>, and so on. A single word is trivially a **word chain** with `k == 1`.
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Return *the **length** of the **longest possible word chain** with words chosen from the given list of* `words`.
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#### Example 1:
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<pre>
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<strong>Input:</strong> words = ["a","b","ba","bca","bda","bdca"]
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<strong>Output:</strong> 4
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<strong>Explanation:</strong> One of the longest word chains is ["a","ba","bda","bdca"].
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</pre>
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#### Example 2:
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<pre>
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<strong>Input:</strong> words = ["xbc","pcxbcf","xb","cxbc","pcxbc"]
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<strong>Output:</strong> 5
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<strong>Explanation:</strong> All the words can be put in a word chain ["xb", "xbc", "cxbc", "pcxbc", "pcxbcf"].
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</pre>
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#### Example 3:
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<pre>
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<strong>Input:</strong> words = ["abcd","dbqca"]
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<strong>Output:</strong> 1
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<strong>Explanation:</strong> The trivial word chain ["abcd"] is one of the longest word chains.
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["abcd","dbqca"] is not a valid word chain because the ordering of the letters is changed.
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</pre>
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#### Constraints:
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* `1 <= words.length <= 1000`
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* `1 <= words[i].length <= 16`
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* `words[i]` only consists of lowercase English letters.
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## Solutions (Python)
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### 1. Solution
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```Python
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class Solution:
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def longestStrChain(self, words: List[str]) -> int:
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chainlen = {word: 1 for word in words}
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for word in sorted(words, key=len):
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for i in range(len(word)):
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pred = word[:i] + word[i + 1:]
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chainlen[word] = max(chainlen[word], chainlen.get(pred, 0) + 1)
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return max(chainlen.values())
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```

‎Problemset/1048-Longest String Chain/README_CN.md

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# 1048. 最长字符串链
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给出一个单词数组 `words` ，其中每个单词都由小写英文字母组成。
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如果我们可以 **不改变其他字符的顺序** ，在 <code>word<sub>A</sub></code> 的任何地方添加 **恰好一个** 字母使其变成 <code>word<sub>B</sub></code> ，那么我们认为 <code>word<sub>A</sub></code> 是 <code>word<sub>B</sub></code> 的 **前身** 。
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* 例如，`"abc"` 是 `"abac"` 的 **前身** ，而 `"cba"` 不是 `"bcad"` 的 **前身**
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**词链**是单词 `[word_1, word_2, ..., word_k]` 组成的序列，`k >= 1`，其中 <code>word<sub>1</sub></code> 是 <code>word<sub>2</sub></code> 的前身，<code>word<sub>2</sub></code> 是 <code>word<sub>3</sub></code> 的前身，依此类推。一个单词通常是 `k == 1` 的 **单词链** 。
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从给定单词列表 `words` 中选择单词组成词链，返回 词链的 **最长可能长度** 。
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#### 示例 1:
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<pre>
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<strong>输入:</strong> words = ["a","b","ba","bca","bda","bdca"]
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<strong>输出:</strong> 4
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<strong>解释:</strong> 最长单词链之一为 ["a","ba","bda","bdca"]
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</pre>
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#### 示例 2:
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<pre>
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<strong>输入:</strong> words = ["xbc","pcxbcf","xb","cxbc","pcxbc"]
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<strong>输出:</strong> 5
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<strong>解释:</strong> 所有的单词都可以放入单词链 ["xb", "xbc", "cxbc", "pcxbc", "pcxbcf"].
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</pre>
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#### 示例 3:
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<pre>
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<strong>输入:</strong> words = ["abcd","dbqca"]
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<strong>输出:</strong> 1
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<strong>解释:</strong> 字链["abcd"]是最长的字链之一。
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["abcd"，"dbqca"]不是一个有效的单词链，因为字母的顺序被改变了。
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</pre>
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#### 提示:
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* `1 <= words.length <= 1000`
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* `1 <= words[i].length <= 16`
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* `words[i]` 仅由小写英文字母组成。
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## 题解 (Python)
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### 1. 题解
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```Python
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class Solution:
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def longestStrChain(self, words: List[str]) -> int:
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chainlen = {word: 1 for word in words}
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for word in sorted(words, key=len):
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for i in range(len(word)):
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pred = word[:i] + word[i + 1:]
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chainlen[word] = max(chainlen[word], chainlen.get(pred, 0) + 1)
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return max(chainlen.values())
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```

‎Problemset/1048-Longest String Chain/Solution.py

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class Solution:
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def longestStrChain(self, words: List[str]) -> int:
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chainlen = {word: 1 for word in words}
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for word in sorted(words, key=len):
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for i in range(len(word)):
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pred = word[:i] + word[i + 1:]
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chainlen[word] = max(chainlen[word], chainlen.get(pred, 0) + 1)
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return max(chainlen.values())

‎README.md

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[1043][1043l]|[Partition Array for Maximum Sum][1043] |![rs]
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[1046][1046l]|[Last Stone Weight][1046] |![py]
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[1047][1047l]|[Remove All Adjacent Duplicates In String][1047] |![py]
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[1048][1048l]|[Longest String Chain][1048] |![py]
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[1051][1051l]|[Height Checker][1051] |![py]
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[1052][1052l]|[Grumpy Bookstore Owner][1052] |![rb]&nbsp;&nbsp;![rs]
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[1053][1053l]|[Previous Permutation With One Swap][1053] |![rs]
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[1043]:Problemset/1043-Partition%20Array%20for%20Maximum%20Sum/README.md#1043-partition-array-for-maximum-sum
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[1046]:Problemset/1046-Last%20Stone%20Weight/README.md#1046-last-stone-weight
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[1047]:Problemset/1047-Remove%20All%20Adjacent%20Duplicates%20In%20String/README.md#1047-remove-all-adjacent-duplicates-in-string
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[1048]:Problemset/1048-Longest%20String%20Chain/README.md#1048-longest-string-chain
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[1051]:Problemset/1051-Height%20Checker/README.md#1051-height-checker
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[1052]:Problemset/1052-Grumpy%20Bookstore%20Owner/README.md#1052-grumpy-bookstore-owner
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[1053]:Problemset/1053-Previous%20Permutation%20With%20One%20Swap/README.md#1053-previous-permutation-with-one-swap
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[1043l]:https://leetcode.com/problems/partition-array-for-maximum-sum/
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[1046l]:https://leetcode.com/problems/last-stone-weight/
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[1047l]:https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string/
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[1048l]:https://leetcode.com/problems/longest-string-chain/
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[1051l]:https://leetcode.com/problems/height-checker/
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[1052l]:https://leetcode.com/problems/grumpy-bookstore-owner/
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[1053l]:https://leetcode.com/problems/previous-permutation-with-one-swap/

‎README_CN.md

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[1043][1043l]|[分隔数组以得到最大和][1043] |![rs]
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[1046][1046l]|[最后一块石头的重量][1046] |![py]
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[1047][1047l]|[删除字符串中的所有相邻重复项][1047] |![py]
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[1048][1048l]|[最长字符串链][1048] |![py]
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[1051][1051l]|[高度检查器][1051] |![py]
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[1052][1052l]|[爱生气的书店老板][1052] |![rb]&nbsp;&nbsp;![rs]
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[1053][1053l]|[交换一次的先前排列][1053] |![rs]
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[1043]:Problemset/1043-Partition%20Array%20for%20Maximum%20Sum/README_CN.md#1043-分隔数组以得到最大和
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[1046]:Problemset/1046-Last%20Stone%20Weight/README_CN.md#1046-最后一块石头的重量
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[1047]:Problemset/1047-Remove%20All%20Adjacent%20Duplicates%20In%20String/README_CN.md#1047-删除字符串中的所有相邻重复项
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[1048]:Problemset/1048-Longest%20String%20Chain/README_CN.md#1048-最长字符串链
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[1051]:Problemset/1051-Height%20Checker/README_CN.md#1051-高度检查器
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[1052]:Problemset/1052-Grumpy%20Bookstore%20Owner/README_CN.md#1052-爱生气的书店老板
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[1053]:Problemset/1053-Previous%20Permutation%20With%20One%20Swap/README_CN.md#1053-交换一次的先前排列
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[1043l]:https://leetcode.cn/problems/partition-array-for-maximum-sum/
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[1046l]:https://leetcode.cn/problems/last-stone-weight/
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[1047l]:https://leetcode.cn/problems/remove-all-adjacent-duplicates-in-string/
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[1048l]:https://leetcode.cn/problems/longest-string-chain/
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[1051l]:https://leetcode.cn/problems/height-checker/
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[1052l]:https://leetcode.cn/problems/grumpy-bookstore-owner/
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[1053l]:https://leetcode.cn/problems/previous-permutation-with-one-swap/

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