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Controlla se la stringa segue l'ordine dei caratteri definito da un modello oppure no | Insieme 2

Data una stringa di input e un modello, controlla se i caratteri nella stringa di input seguono lo stesso ordine determinato dai caratteri presenti nel modello. Supponiamo che non ci saranno caratteri duplicati nel modello.
Viene pubblicata un'altra soluzione allo stesso problema Qui .
Esempi:  
 

Input: string = 'engineers rock' pattern = 'er'; Output: true All 'e' in the input string are before all 'r'. Input: string = 'engineers rock' pattern = 'egr'; Output: false There are two 'e' after 'g' in the input string. Input: string = 'engineers rock' pattern = 'gsr'; Output: false There are one 'r' before 's' in the input string.


 




L'idea qui è di ridurre la stringa data al modello dato. Per i caratteri indicati nel modello manteniamo solo i caratteri corrispondenti nella stringa. Nella nuova stringa cancelliamo i caratteri ripetuti continui. La stringa modificata dovrebbe quindi essere uguale al modello fornito. Infine confrontiamo la stringa modificata con il modello fornito e restituiamo di conseguenza true o false.
Illustrazione: 
 

str = 'bfbaeadeacc' pat[] = 'bac' 1) Remove extra characters from str (characters that are not present in pat[] str = 'bbaaacc' [f e and d are removed] 3) Removed consecutive repeating occurrences of characters str = 'bac' 4) Since str is same as pat[] we return true


Di seguito è riportata l'implementazione dei passaggi precedenti.
 

C++ 
// C++ code for the above approach #include    #include  using namespace std; bool followsPattern(string str string pattern) {  // Insert all characters of pattern in a hash set  unordered_set<char> patternSet;  for (int i = 0; i < pattern.length(); i++) {  patternSet.insert(pattern[i]);  }  // Build modified string (string with characters only from pattern are taken)  string modifiedStr = str;  for (int i = str.length() - 1; i >= 0; i--) {  if (patternSet.find(str[i]) == patternSet.end()) {  modifiedStr.erase(i 1);  }  }  // Remove more than one consecutive occurrences of pattern characters from modified string  for (int i = modifiedStr.length() - 1; i > 0; i--) {  if (modifiedStr[i] == modifiedStr[i - 1]) {  modifiedStr.erase(i 1);  }  }  // After above modifications the length of modified string must be same as pattern length  if (pattern.length() != modifiedStr.length()) {  return false;  }  // And pattern characters must also be same as modified string characters  for (int i = 0; i < pattern.length(); i++) {  if (pattern[i] != modifiedStr[i]) {  return false;  }  }  return true; } int main() {  string str = 'engineers rock';  string pattern = 'er';  cout << 'Expected: true Actual: ' << followsPattern(str pattern) << endl;  str = 'engineers rock';  pattern = 'egr';  cout << 'Expected: false Actual: ' << followsPattern(str pattern) << endl;  str = 'engineers rock';  pattern = 'gsr';  cout << 'Expected: false Actual: ' << followsPattern(str pattern) << endl;  str = 'engineers rock';  pattern = 'eger';  cout << 'Expected: true Actual: ' << followsPattern(str pattern) << endl;  return 0; } // This code is contributed by adityashatmfh
Java 
// Java program to check if characters of a string follow // pattern defined by given pattern. import java.util.*; public class OrderOfCharactersForPattern {  public static boolean followsPattern(String str String pattern)  {  // Insert all characters of pattern in a hash set  Set<Character> patternSet = neHashSet<>();  for (int i=0; i<pattern.length(); i++)  patternSet.add(pattern.charAt(i));  // Build modified string (string with characters only from  // pattern are taken)  StringBuilder modifiedString = new StringBuilder(str);  for (int i=str.length()-1; i>=0; i--)  if (!patternSet.contains(modifiedString.charAt(i)))  modifiedString.deleteCharAt(i);  // Remove more than one consecutive occurrences of pattern  // characters from modified string.  for (int i=modifiedString.length()-1; i>0; i--)  if (modifiedString.charAt(i) == modifiedString.charAt(i-1))  modifiedString.deleteCharAt(i);  // After above modifications the length of modified string  // must be same as pattern length  if (pattern.length() != modifiedString.length())  return false;  // And pattern characters must also be same as modified string  // characters  for (int i=0; i<pattern.length(); i++)  if (pattern.charAt(i) != modifiedString.charAt(i))  return false;  return true;  }  // Driver program  int main()  {  String str = 'engineers rock';  String pattern = 'er';  System.out.println('Expected: true Actual: ' +  followsPattern(str pattern));  str = 'engineers rock';  pattern = 'egr';  System.out.println('Expected: false Actual: ' +  followsPattern(str pattern));  str = 'engineers rock';  pattern = 'gsr';  System.out.println('Expected: false Actual: ' +  followsPattern(str pattern));  str = 'engineers rock';  pattern = 'eger';  System.out.println('Expected: true Actual: ' +  followsPattern(str pattern));  return 0;  } }
Python3 
# Python3 program to check if characters of  # a string follow pattern defined by given pattern. def followsPattern(string pattern): # Insert all characters of pattern in a hash set patternSet = set() for i in range(len(pattern)): patternSet.add(pattern[i]) # Build modified string (string with characters  # only from pattern are taken) modifiedString = string for i in range(len(string) - 1 -1 -1): if not modifiedString[i] in patternSet: modifiedString = modifiedString[:i] +  modifiedString[i + 1:] # Remove more than one consecutive occurrences  # of pattern characters from modified string. for i in range(len(modifiedString) - 1 0 -1): if modifiedString[i] == modifiedString[i - 1]: modifiedString = modifiedString[:i] +  modifiedString[i + 1:] # After above modifications the length of  # modified string must be same as pattern length if len(pattern) != len(modifiedString): return False # And pattern characters must also be same  # as modified string characters for i in range(len(pattern)): if pattern[i] != modifiedString[i]: return False return True # Driver Code if __name__ == '__main__': string = 'engineers rock' pattern = 'er' print('Expected: true Actual:' followsPattern(string pattern)) string = 'engineers rock' pattern = 'egr' print('Expected: false Actual:' followsPattern(string pattern)) string = 'engineers rock' pattern = 'gsr' print('Expected: false Actual:' followsPattern(string pattern)) string = 'engineers rock' pattern = 'eger' print('Expected: true Actual:' followsPattern(string pattern)) # This code is contributed by # sanjeev2552
C# 
// C# program to check if characters of a string follow // pattern defined by given pattern. using System; using System.Collections.Generic; using System.Text; class GFG {  public static bool followsPattern(String str String pattern)  {  // Insert all characters of pattern in a hash set  HashSet<char> patternSet = new HashSet<char>();  for (int i = 0; i < pattern.Length; i++)  patternSet.Add(pattern[i]);  // Build modified string (string with characters   // only from pattern are taken)  StringBuilder modifiedString = new StringBuilder(str);  for (int i = str.Length - 1; i >= 0; i--)  if (!patternSet.Contains(modifiedString[i]))  modifiedString.Remove(i 1);  // Remove more than one consecutive occurrences of pattern  // characters from modified string.  for (int i = modifiedString.Length - 1; i > 0; i--)  if (modifiedString[i] == modifiedString[i - 1])  modifiedString.Remove(i 1);  // After above modifications the length of modified string  // must be same as pattern length  if (pattern.Length != modifiedString.Length)  return false;  // And pattern characters must also be same   // as modified string characters  for (int i = 0; i < pattern.Length; i++)  if (pattern[i] != modifiedString[i])  return false;  return true;  }  // Driver program  public static void Main(String[] args)  {  String str = 'engineers rock';  String pattern = 'er';  Console.WriteLine('Expected: true Actual: ' +  followsPattern(str pattern));  str = 'engineers rock';  pattern = 'egr';  Console.WriteLine('Expected: false Actual: ' +  followsPattern(str pattern));  str = 'engineers rock';  pattern = 'gsr';  Console.WriteLine('Expected: false Actual: ' +  followsPattern(str pattern));  str = 'engineers rock';  pattern = 'eger';  Console.WriteLine('Expected: true Actual: ' +  followsPattern(str pattern));  } } // This code is contributed by 29AjayKumar
JavaScript 
<script> // Javascript program to check if characters of a string follow // pattern defined by given pattern. function followsPattern(str pattern) {  // Insert all characters of pattern in a hash set  let patternSet = new Set();  for (let i=0; i<pattern.length; i++)  patternSet.add(pattern[i]);    // Build modified string (string with characters only from  // pattern are taken)  let modifiedString = (str).split('');  for (let i=str.length-1; i>=0; i--)  if (!patternSet.has(modifiedString[i]))  modifiedString.splice(i1);    // Remove more than one consecutive occurrences of pattern  // characters from modified string.  for (let i=modifiedString.length-1; i>0; i--)  if (modifiedString[i] == modifiedString[i-1])  modifiedString.splice(i1);    // After above modifications the length of modified string  // must be same as pattern length  if (pattern.length != modifiedString.length)  return false;    // And pattern characters must also be same as modified string  // characters  for (let i=0; i<pattern.length; i++)  if (pattern[i] != modifiedString[i])  return false;    return true; } // Driver program let str = 'engineers rock'; let pattern = 'er'; document.write('Expected: true Actual: ' +  followsPattern(str pattern)+'  
'); str = 'engineers rock'; pattern = 'egr'; document.write('Expected: false Actual: ' +  followsPattern(str pattern)+'  
'); str = 'engineers rock'; pattern = 'gsr'; document.write('Expected: false Actual: ' +  followsPattern(str pattern)+'  
'); str = 'engineers rock'; pattern = 'eger'; document.write('Expected: true Actual: ' +  followsPattern(str pattern)+'  
'); // This code is contributed by rag2127 </script>

Produzione:  
 



Expected: true Actual: true Expected: false Actual: false Expected: false Actual: false Expected: true Actual: true


Complessità temporale: La complessità temporale delle implementazioni di cui sopra è in realtà O(mn + n^2) poiché utilizziamo deleteCharAt() per rimuovere i caratteri. Possiamo ottimizzare la soluzione di cui sopra per lavorare in tempo lineare. Invece di usare deleteCharAr() possiamo creare una stringa vuota e aggiungervi solo i caratteri richiesti.
StringBuilder viene utilizzato per operare sulla stringa di input. Questo perché StringBuilder è mutabile mentre String è un oggetto immutabile. Per creare una nuova stringa è necessario O(n) spazio, quindi lo spazio extra è O(n).
Abbiamo discusso altri due approcci per risolvere questo problema. 
Controlla se la stringa segue l'ordine dei caratteri definito da un modello oppure no | Insieme 1  
Controlla se la stringa segue l'ordine dei caratteri definito da un modello oppure no | Insieme 3