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| 1 | +# 763. Partition Labels |
| 2 | + |
| 3 | +**<font color=red>难度: Medium</font>** |
| 4 | + |
| 5 | +## 刷题内容 |
| 6 | + |
| 7 | +> 原题连接 |
| 8 | +
|
| 9 | +* https://leetcode.com/problems/partition-labels/description/ |
| 10 | + |
| 11 | +> 内容描述 |
| 12 | +
|
| 13 | +``` |
| 14 | +
|
| 15 | +A string S of lowercase letters is given. We want to partition this string into as many parts as possible so that each letter appears in at most one part, and return a list of integers representing the size of these parts. |
| 16 | +
|
| 17 | +Example 1: |
| 18 | +Input: S = "ababcbacadefegdehijhklij" |
| 19 | +Output: [9,7,8] |
| 20 | +Explanation: |
| 21 | +The partition is "ababcbaca", "defegde", "hijhklij". |
| 22 | +This is a partition so that each letter appears in at most one part. |
| 23 | +A partition like "ababcbacadefegde", "hijhklij" is incorrect, because it splits S into less parts. |
| 24 | +Note: |
| 25 | +
|
| 26 | +S will have length in range [1, 500]. |
| 27 | +S will consist of lowercase letters ('a' to 'z') only. |
| 28 | +``` |
| 29 | + |
| 30 | +## 解题方案 |
| 31 | + |
| 32 | +> 思路 1 |
| 33 | +******- 时间复杂度: O(N)******- 空间复杂度: O(1)****** |
| 34 | + |
| 35 | + |
| 36 | +从第一个字母开始,只要我们包含了这个字母,那么它在S中出现的最后一次我们也要包含进去,当前出现过的所有的字母,我们每次都要更新最后出现的那一次, |
| 37 | +并且要一直遍历到其最后一次,这样我们可以维护一个当前至少需要遍历到的end,然后只要出现一个新的字母, |
| 38 | +就更新一个这个end(取新字母最后出现idx和end之间的大者),最后,当我们遍历到一个idx的时候,如果这个idx与我们的end相等, |
| 39 | +说明截止当前所有出现的字母都在我们的[start, end]字串当中了,直接append它的长度到res中,一直遍历到最后,返回res |
| 40 | + |
| 41 | +beats 98.39% |
| 42 | + |
| 43 | +```python |
| 44 | +class Solution(object): |
| 45 | + def partitionLabels(self, S): |
| 46 | + """ |
| 47 | + :type S: str |
| 48 | + :rtype: List[int] |
| 49 | + """ |
| 50 | + if not S or len(S) == 0: |
| 51 | + return True |
| 52 | + lookup = {} |
| 53 | + for i, c in enumerate(S): |
| 54 | + lookup[c] = i |
| 55 | + start, end, res = 0, 0, [] |
| 56 | + for i, c in enumerate(S): |
| 57 | + end = max(end, lookup[c]) |
| 58 | + if i == end: |
| 59 | + res.append(end-start+1) |
| 60 | + start = i + 1 |
| 61 | + return res |
| 62 | +``` |
| 63 | + |
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