Given a string, we can "shift" each of its letter to its successive letter, for example: "abc" -> "bcd". We can keep "shifting" which forms the sequence:
"abc" -> "bcd" -> ... -> "xyz"
Given a list of strings which contains only lowercase alphabets, group all strings that belong to the same shifting sequence.
For example, given: ["abc", "bcd", "acef", "xyz", "az", "ba", "a", "z"],
A solution is:
[
["abc","bcd","xyz"],
["az","ba"],
["acef"],
["a","z"]
]
1 class Solution {
2 public:
3 string help(string word) {
4 for (int i = 1, n = word.size(); i < n; i++) {
5 word[i] = word[i] - word[0] + 'a';
6 while (word[i] < 'a') word[i] += 26;
7 }
8 word[0] = 'a';
9 return word;
10 }
11 vector<vector<string>> groupStrings(vector<string>& strings) {
12 unordered_map<string, int> dict;
13 vector<vector<string> > res;
14 for (int i = 0, n = strings.size(); i < n; i++) {
15 string base = help(strings[i]);
16 if (dict.count(base) == 0) {
17 dict.insert(make_pair(base, res.size()));
18 vector<string> subGroup(1, strings[i]);
19 res.push_back(subGroup);
20 }
21 else res[dict[base]].push_back(strings[i]);
22 }
23 return res;
24 }
25 };