LeetCode 290. Word Pattern

Given a pattern and a string str, find if str follows the same pattern.

Here follow means a full match, such that there is a bijection between a letter inpattern and anon-empty word in str.

Examples:

1. pattern = "abba", str = "dog cat cat dog" should return true ::::: map[a] = 1, map[dog] = 1;  map[b] = 1, map[cat] = 1; map[b] = 2, map[cat] = 2; map[a] = 2, map[dog] = 2 ---->true
   
2. pattern = "abba", str = "dog cat cat fish" should return false. ::::: map[a] = 1, map[dog] = 1'; map[b] = 1, map[cat] = 1; map[b] = 2, map[cat] = 2; map[a] = 2, map[fish] = 1 ----> false
   
3. pattern = "aaaa", str = "dog cat cat dog" should return false. ::::: map[a] = 1, map[dog] = 1; map[a] = 2, map[cat] = 1 ---->false
   
4. pattern = "abba", str = "dog dog dog dog" should return false. :::: map[a] = 1, map[dog] = 1; map[b] = 1, map[dog] = 2 ---> false
   

It will cost a lot of energy if trying to split the words..... it is good to use stringstream!

    bool wordPattern(string pattern, string str) {        vector<string> words;        stringstream s(str);        string word;        while(s >> word) words.push_back(word);                if(words.size() != pattern.size()) return false;        unordered_map<string ,int> map_1;        unordered_map<char, int> map_2;                for(int i = 0; i < pattern.size(); ++i) {            if(map_1[words[i]] || map_2[pattern[i]]) {                if(map_1[words[i]] != map_2[pattern[i]]) return false;            } else {                map_1[words[i]]++;                map_2[pattern[i]]++;            }        }        return true;    }

Another way:

#include <string>#include <iostream>#include <sstream>#include <unordered_map>#include <unordered_set>using namespace std;bool wordPattern(string pattern, string words) {  int cnt = 0;  stringstream in(words);  string word;  /* we only need to set up one map. char to string.*/  /* the words need a set to check if it is already there.*/  unordered_map<char, string> hash1;  unordered_set<string> hash2;  while(in >> word) {    if(cnt == pattern.size()) return false;    if(hash1.find(pattern[cnt]) == hash1.end() && hash2.find(word) == hash2.end()) {      hash1.insert({pattern[cnt], word});      hash2.insert(word);    } else if(hash1[pattern[cnt]] != word) return false;    cnt++;  }  return cnt == pattern.size();}int main(void) {  cout << wordPattern("abc", "word, words, wordses") << endl;  cout << wordPattern("aab", "word word words") << endl;  cout << wordPattern("aab", "word words words") << endl;  cout << wordPattern("aba", "word words word") << endl;}