What is the core pattern for solving the Partition String problem?

The core pattern for solving the Partition String problem is using a hash table to track the characters in the current segment and simulating the partitioning process.

How do you optimize the solution for time and space complexity in the Partition String problem?

The solution is optimized by using a hash table to track characters in linear time, which reduces the need for nested loops. The space complexity is minimal, proportional to the number of unique characters.

What is the expected output for input 'abbccccd' in the Partition String problem?

The expected output is ["a", "b", "bc", "c", "cc", "d"]. Each segment contains unique characters without repetition.

Can I use a different data structure other than a hash table for solving this problem?

Yes, you can use a Trie, but the hash table approach is more efficient for this problem. A Trie would generally have higher overhead due to its more complex structure.

What should I do if I encounter a string where all characters are unique in the Partition String problem?

In this case, each character will form its own segment. The output will be an array of the individual characters.

#3597

Medium

auto_awesome哈希·表·结合·string

LeetCode 题解工作台

分割字符串

给你一个字符串 s ，按照以下步骤将其分割为互不相同的段：从下标 0 开始构建一个段。逐字符扩展当前段，直到该段之前未曾出现过。只要当前段是唯一的，就将其加入段列表，标记为已经出现过，并从下一个下标开始构建新的段。重复上述步骤，直到处理完整个字符串 s 。返回字符串数组 segment…

哈希表字符串字典树模拟

题目描述

给你一个字符串 s，按照以下步骤将其分割为 互不相同的段 ：

从下标 0 开始构建一个段。
逐字符扩展当前段，直到该段之前未曾出现过。
只要当前段是唯一的，就将其加入段列表，标记为已经出现过，并从下一个下标开始构建新的段。
重复上述步骤，直到处理完整个字符串 s。

返回字符串数组 segments，其中 segments[i] 表示创建的第 i 段。

示例 1：

输入： s = "abbccccd"

输出： ["a","b","bc","c","cc","d"]

解释：

下标	添加后的段	已经出现过的段	当前段是否已经出现过？	新段	更新后已经出现过的段
0	"a"	[]	否	""	["a"]
1	"b"	["a"]	否	""	["a", "b"]
2	"b"	["a", "b"]	是	"b"	["a", "b"]
3	"bc"	["a", "b"]	否	""	["a", "b", "bc"]
4	"c"	["a", "b", "bc"]	否	""	["a", "b", "bc", "c"]
5	"c"	["a", "b", "bc", "c"]	是	"c"	["a", "b", "bc", "c"]
6	"cc"	["a", "b", "bc", "c"]	否	""	["a", "b", "bc", "c", "cc"]
7	"d"	["a", "b", "bc", "c", "cc"]	否	""	["a", "b", "bc", "c", "cc", "d"]

因此，最终输出为 ["a", "b", "bc", "c", "cc", "d"]。

示例 2：

输入： s = "aaaa"

输出： ["a","aa"]

解释：

下标	添加后的段	已经出现过的段	当前段是否已经出现过？	新段	更新后已经出现过的段
0	"a"	[]	否	""	["a"]
1	"a"	["a"]	是	"a"	["a"]
2	"aa"	["a"]	否	""	["a", "aa"]
3	"a"	["a", "aa"]	是	"a"	["a", "aa"]

因此，最终输出为 ["a", "aa"]。

提示：

1 <= s.length <= 10⁵
s 仅包含小写英文字母。

lightbulb

解题思路

方法一：哈希表 + 模拟

我们可以用一个哈希表 $\textit{vis}$ 来记录已经出现过的段。然后我们遍历字符串 $s$ ，逐字符构建当前段 $t$ ，直到该段之前未曾出现过。每当我们构建出一个新的段时，就将其加入到结果列表中，并将其标记为已经出现过。

遍历结束后，返回结果列表即可。

时间复杂度 $O(n \times \sqrt{n})$ ，空间复杂度 $O(n)$ ，其中 $n$ 是字符串 $s$ 的长度。

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class Solution:
    def partitionString(self, s: str) -> List[str]:
        vis = set()
        ans = []
        t = ""
        for c in s:
            t += c
            if t not in vis:
                vis.add(t)
                ans.append(t)
                t = ""
        return ans

speed

复杂度分析

指标	值
时间	Depends on the final approach
空间	Depends on the final approach

psychology

面试官常问的追问

外企场景

question_mark
Does the candidate understand how to handle string segmentation efficiently?
question_mark
Is the candidate able to manage a hash table for tracking characters in real-time?
question_mark
Can the candidate explain the trade-offs involved in choosing hash tables over other data structures?

warning

常见陷阱

外企场景

error
Not properly managing the segments when characters repeat, leading to incorrect partitions.
error
Using a brute force approach with nested loops, which results in higher time complexity.
error
Failing to handle edge cases like strings with all unique characters or all repeated characters.

swap_horiz

进阶变体

外企场景

arrow_right_alt
Modify the problem to use uppercase letters only.
arrow_right_alt
Extend the problem to allow a custom rule for segment uniqueness, such as allowing certain characters to repeat a limited number of times.
arrow_right_alt
Solve the problem with a Trie data structure instead of a hash table.

help

常见问题

外企场景

继续练习

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