49.Group Anagrams

题目描述

Given an array of strings strs, group the anagrams together. You can return the answer in any order.

An Anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once.

Example 1:
Input: strs = [“eat”,”tea”,”tan”,”ate”,”nat”,”bat”]
Output: [[“bat”],[“nat”,”tan”],[“ate”,”eat”,”tea”]]

Example 2:
Input: strs = [“”]
Output: [[“”]]

Example 3:
Input: strs = [“a”]
Output: [[“a”]]

Constraints:

1 <= strs.length <= 104
0 <= strs[i].length <= 100
strs[i] consists of lower-case English letters.

我的解法

解题思路

不太会做的一题，看了下题解，可以用hashmap来存放整个字符串数组，key是经过排序的string，value是一个字符串数组，包含来所有当前字母组合的字符串。

实现代码

class Solution {
public:
    vector<vector<string>> groupAnagrams(vector<string>& strs) {
        vector<vector<string>> res;
        unordered_map<string, vector<string>> m;
        for (const auto& str : strs){
            auto key = str;
            sort(key.begin(), key.end());
            m[key].push_back(str);
        }        
        for (const auto& im : m)
            res.push_back(im.second);
        return res;
    }
};