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Commit 280420a

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Prob 181: Word pattern problem
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‎README.md‎

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| Current Status| Stats |
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| :------------: | :----------: |
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| Total Problems | 180 |
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| Total Problems | 181 |
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</center>
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| Remove the minimum number of invalid parentheses in order to make the input string valid. Return all possible results. Note: The input string may contain letters other than the parentheses ( and ) | [remove_invalid_parenthesis.cpp](leet_code_problems/remove_invalid_parenthesis.cpp)|
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| Given an array and a value, remove all instances of that value in-place and return the new length. Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory. The order of elements can be changed. It doesn't matter what you leave beyond the new length.| [remove_element.cpp](leet_code_problems/remove_element.cpp)|
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| Find intersection of two arrays/vectors, Given two vectors find the result of their interaction. The result should only contain unique characters and can be in any order|[intersection_of_array.cpp](leet_code_problems/intersection_of_array.cpp)|
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| 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 in pattern and a non-empty word in str. example:
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pattern = "abba", str = "dog cat cat dog" should return true.
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pattern = "abba", str = "dog cat cat fish" should return false.
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pattern = "aaaa", str = "dog cat cat dog" should return false.
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pattern = "abba", str = "dog dog dog dog" should return false.| [word_pattern.cpp](leet_code_problems/word_pattern.cpp)|

‎leet_code_problems/word_pattern.cpp‎

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/*
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*
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* Given a pattern and a string str, find if str follows the same pattern.
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* Here follow means a full match, such that there is a bijection between a letter in pattern and a non-empty word in str.
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* Examples:
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* pattern = "abba", str = "dog cat cat dog" should return true.
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* pattern = "abba", str = "dog cat cat fish" should return false.
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* pattern = "aaaa", str = "dog cat cat dog" should return false.
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* pattern = "abba", str = "dog dog dog dog" should return false.
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* Notes:
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* You may assume pattern contains only lowercase letters, and str
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* contains lowercase letters separated by a single space.
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*
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* Approach:
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*
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* Split the string into words, and then map it to each character of the patterns as _we move.
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* If the character is being mapped to multiple words, or a word is being mapped to multiple
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* character, then the str is not following pattern.
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*/
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#include <iostream>
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#include <vector>
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#include <sstream>
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#include <unordered_map>
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#include <unordered_set>
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bool match_pattern(const std::string& str, const std::string& pattern)
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{
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// split string to words
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std::istringstream iss(str);
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std::vector<std::string> words(std::istream_iterator<std::string>{iss},
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std::istream_iterator<std::string>());
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if (words.size() != pattern.size()) {
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return false;
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}
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std::unordered_map<char, std::string> map;
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std::unordered_set<std::string> set;
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for (int i = 0; i < pattern.size(); ++i) {
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if (map.find(pattern[i]) != map.end()) {
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// pattern is already mapped to some other string.
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if (words[i] != map[pattern[i]]) {
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return false;
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}
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} else {
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// word is already mapped to some other string.
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if (set.count(words[i])) {
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return false;
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} else {
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map[pattern[i]] = words[i];
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set.insert(words[i]);
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}
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}
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}
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return true;
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}
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int main() {
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std::string pattern{"abba"};
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std::string str{"dog cat cat dog"};
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std::cout << "Pattern : " << pattern << std::endl;
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std::cout << "String :" << str << std::endl;
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bool r = match_pattern(str, pattern);
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std::string result = (r) ? "true" : "false";
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std::cout << "Result :" << result << std::endl;
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pattern = "aaaa";
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std::cout << "Pattern : " << pattern << std::endl;
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std::cout << "String :" << str << std::endl;
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r = match_pattern(str, pattern);
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result = (r) ? "true" : "false";
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std::cout << "Result :" << result << std::endl;
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return 0;
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}

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