[leetcode][hash] Anagrams

来源：互联网发布：旅游软件排行编辑：程序博客网时间：2024/05/16 08:31

题目;

Given an array of strings, return all groups of strings that are anagrams.

Note: All inputs will be in lower-case.

v1 76ms

class Solution {public:    //将单词按字母顺序排序后作为hash的key，字符串在strs中的下标组成的vector作为valuevector<string> anagrams(vector<string>& strs) {vector<string> res;map<string, vector<int> > hashTable;for (int i = 0; i < strs.size(); ++i){string s = strs[i];sort(s.begin(), s.end());map<string, vector<int> >::iterator iter = hashTable.find(s);if (iter != hashTable.end()){(iter->second).push_back(i);}else{vector<int> vTmp;vTmp.push_back(i);hashTable[s] = vTmp;}}for (map<string, vector<int> >::iterator iter = hashTable.begin(); iter != hashTable.end(); ++iter){if ((iter->second).size() > 1){for (int i = 0; i < (iter->second).size(); ++i){res.push_back(strs[(iter->second)[i]]);}}}return res;}};

v2 68ms

class Solution {public://将单词按字母顺序排序后作为hash的key，value等于排序后单词第一次出现大的下标，当第二次出现时value置为-1防止重复再结果中插入第一出现的单词vector<string> anagrams(vector<string>& strs) {vector<string> res;map<string, int> hashTable;for (int i = 0; i < strs.size(); ++i){string s = strs[i];sort(s.begin(), s.end());map<string,int>::iterator iter = hashTable.find(s);if (iter != hashTable.end()){if (iter->second != -1){res.push_back(strs[iter->second]);iter->second = -1;}res.push_back(strs[i]);}else{hashTable[s] = i;}}return res;}};

v3 40ms

class Solution {public:const int alphabetList[26] = { 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101 };vector<string> anagrams(vector<string>& strs) {vector<string> res;map<long long, int> hashTable;for (int i = 0; i < strs.size(); ++i){long long multi = 1;for (int j = 0; j < strs[i].size(); ++j){multi *= alphabetList[strs[i][j]-'a'];}map<long long, int>::iterator iter = hashTable.find(multi);if (iter != hashTable.end()){if (iter->second != -1){res.push_back(strs[iter->second]);iter->second = -1;}res.push_back(strs[i]);}else{hashTable[multi] = i;}}return res;}};

每一个字母用一个质数代表，用单词中每个字符对应的质数相乘的积作为hash的key（这样查找时不需要比较单词的每一个字符，效率大大提高了），value的意义同上

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