763. Partition Labels
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题目描述:
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.
Example 1:
Input: S = "ababcbacadefegdehijhklij" Output: [9,7,8] Explanation: The partition is "ababcbaca", "defegde", "hijhklij". This is a partition so that each letter appears in at most one part. A partition like "ababcbacadefegde", "hijhklij" is incorrect, because it splits S into less parts.
Note:
S
will have length in range[1, 500]
.S
will consist of lowercase letters (‘a‘
to‘z‘
) only.
解题思路:
遍历S,找到S[i]在S中最后出现的位置j,此时遍历i到j中的每个元素S[index],若S[index]在S中最后出现的位置大于j时,j等于S[index]在S中最后出现的位置,当index等于j时结束内循环。
预先记录每个字母在S最后出现的位置可以提高运算时间。
代码:
1 class Solution { 2 public: 3 vector<int> partitionLabels(string S) { 4 vector<int> res; 5 for (int i = 0; i < S.size();) { 6 size_t j = S.find_last_of(S[i]); 7 if (i == j) { 8 res.push_back(1); 9 i += 1; 10 continue; 11 } 12 for (int index = i + 1; index <= j; ++index) { 13 size_t tmp = S.find_last_of(S[index]); 14 if (tmp > j) 15 j = tmp; 16 } 17 res.push_back(j-i+1); 18 i = j + 1; 19 } 20 return res; 21 } 22 };
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