[leetcode-763-Partition Labels]

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.

思路：

1.第一次扫描字符串，记录每个字符最后出现的索引。

2.第二次扫描，如果当前索引是该字符的最后出现的索引，则记录当前分割段的长度。

vector<int> partitionLabels(string S)
 {
    vector<int> ret;
    map<char,int>mp;
    for(int i=0;i<S.size();i++)mp[S[i]] = i;
    int last = 0,start = -1;
    for(int i=0;i<S.size();i++)
    {
        last = max(last,mp[S[i]]);
        if(last == i)
        {
            ret.push_back(last - start);
            start = last;
        }
    }
    return ret;    
 }

参考：

https://discuss.leetcode.com/topic/117141/java-2-pass-o-n-time-o-1-space-extending-end-pointer-solution