title
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.
solution
分隔字符串使同种字符出现在一起, 贪心算法
class Solution {
public:
vector<int> partitionLabels(string S) {
unordered_map<char, int> map;
for (int i=0; i<S.size(); i++) {
map[S[i]] = i;
}
vector<int> res;
int start = 0;
for (int i=0; i<S.size(); i++) {
int end = map[S[start]];
for (; i<end; i++) {
if (map[S[i]] > end) {
end = map[S[i]];
}
}
res.push_back(end-start+1);
start = end+1;
}
return res;
}
};
下面等价
class Solution {
public:
vector<int> partitionLabels(string S) {
unordered_map<char, int> map1;
for (int i = 0; i < S.length(); i++) {
map1[S[i]] = i;
}
vector<int> res;
int j = 0, start = 0;
for (int i = 0; i < S.length(); i++) {
j = max(j, map1[S[i]]);
if (i == j) {
res.push_back(i - start + 1);
start = i + 1;
}
}
return res;
}
};