# 0249. Group Shifted Strings

<https://leetcode.com/problems/group-shifted-strings>

## Description

We can shift a string by shifting each of its letters to its successive letter.

* For example, `"abc"` can be shifted to be `"bcd"`.

We can keep shifting the string to form a sequence.

* For example, we can keep shifting `"abc"` to form the sequence: `"abc" -> "bcd" -> ... -> "xyz"`.

Given an array of strings `strings`, group all `strings[i]` that belong to the same shifting sequence. You may return the answer in **any order**.

**Example 1:**

```
**Input:** strings = ["abc","bcd","acef","xyz","az","ba","a","z"]
**Output:** [["acef"],["a","z"],["abc","bcd","xyz"],["az","ba"]]
```

**Example 2:**

```
**Input:** strings = ["a"]
**Output:** [["a"]]
```

**Constraints:**

* `1 <= strings.length <= 200`
* `1 <= strings[i].length <= 50`
* `strings[i]` consists of lowercase English letters.

## ac

```java
class Solution {
    public List<List<String>> groupStrings(String[] strings) {
        List<List<String>> res = new ArrayList<List<String>>();

        Map<Integer, List<List<String>>> map = new HashMap<Integer, List<List<String>>>();

        // group by len
        for (String s : strings) {
            int len = s.length();
            if (!map.containsKey(len)){
                map.put(len, new ArrayList<List<String>>());
                List<String> tmpList = new ArrayList<String>();;
                tmpList.add(s);
                map.get(len).add(tmpList);
            } else {
                boolean added = false;
                for (List<String> list : map.get(len)) {
                    if (same(list.get(0), s)) {
                        list.add(s);
                        added = true;
                        break;
                    }
                }
                if (!added) {
                    List<String> tmpList = new ArrayList<String>();
                    tmpList.add(s);
                    map.get(len).add(tmpList);
                }
            }
        }

        // add to result
        for (List<List<String>> lists : map.values()) {
            for (List<String> list : lists) res.add(list);
        }

        return res;
    }

    private boolean same(String s1, String s2) {
        int diff = (s2.charAt(0) - s1.charAt(0) + 26) % 26;
        for (int i = 1; i < s1.length(); i++) {
            int num1 = s1.charAt(i) - 'a';
            int num2 = s2.charAt(i) - 'a';
            if ( (num1 + diff) % 26 != num2 ) return false;
        }
        return true;
    }
}
```

## ac2: transform every word back to base status

```java
class Solution {
    public List<List<String>> groupStrings(String[] strings) {
        List<List<String>> res = new ArrayList<List<String>>();

        Map<String, List<String>> map = new HashMap<String, List<String>>();

        for (String s : strings) {
            // get base key
            String key = "";
            int diff = s.charAt(0) - 'a';
            for (int i = 0; i < s.length(); i++) {
                char c = (char) (s.charAt(i) - diff);
                if (c < 'a') c += 26;
                key += c;
            }

            // add to map
            if (!map.containsKey(key)) map.put(key, new ArrayList<String>());
            map.get(key).add(s);
        }

        // add to result return
        for (List<String> list : map.values()) {
            res.add(list);
        }

        return res;
    }
}
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://jaywin.gitbook.io/leetcode/solutions/0249-group-shifted-strings.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.