Patterns and custom keys

Questions 1 to 5 of 8

1. 1. Why does the isomorphic check use two maps instead of one?

   Letters that repeat in the first string need the second mapThe case where both strings are empty needs a second map to return trueTwo different letters in the first string can share one partner, such as ab and aa, and only the second map catches thatA pair of strings with different lengths needs a second map to be rejected
2. 2. What does this program print? ``cpp #include <iostream> #include <string> #include <unordered_map> using namespace std; bool isIsomorphic(const string& s, const string& t) { if (s.size() != t.size()) return false; unordered_map<char, char> sToT; unordered_map<char, char> tToS; for (size_t i = 0; i < s.size(); ++i) { char a = s[i]; char b = t[i]; auto forward = sToT.find(a); if (forward != sToT.end() && forward->second != b) return false; auto backward = tToS.find(b); if (backward != tToS.end() && backward->second != a) return false; sToT[a] = b; tToS[b] = a; } return true; } int main() { cout << boolalpha; cout << isIsomorphic("abab", "cdcd") << " " << isIsomorphic("abc", "xxy") << "\n"; } ``

   true truefalse falsetrue falsefalse true
3. 3. What is wrong with the line that splits the sentence? ``cpp #include <string> #include <vector> using namespace std; int main() { string text = "dog cat cat dog"; vector<string> words = text.split(' '); return static_cast<int>(words.size()); } ``

   The vector must be declared as vector<char>The return type of main must be voidThe static_cast on the size is not allowedstd::string has no split member, so the code does not compile, and the words should be read with istringstream
4. 4. Does the pattern abba match the sentence dog cat cat fish? True or false?

   True, because the lengths match, four letters and four wordsFalse, because the last a would have to stand for fish, but a already stands for dog
5. 5. Inside the check, why does the lesson look up keys with find instead of map[key]?

   find is the only way to read a value from an unordered_mapmap[key] returns a copy of the value, and a copy cannot be comparedfind works only on std::map, not on unordered_mapmap[key] adds an entry with a default value when the key is missing, so the check would change the map