Koska a merkkijono s tehtävänä on löytää minimi hahmoja liitetty (lisäys loppuun) tehdä merkkijonopalindromi.
Esimerkkejä:
Syöte : s = 'tehty'
Lähtö : 2
Selitys: Voimme tehdä merkkijonopalindromista "abede". ei ' lisäämällä ei merkkijonon lopussa.
Syöte :s = 'aabb'
Lähtö : 2
Selitys: Voimme tehdä merkkijonopalindromin nimellä'aabb aa ' lisäämällä aa merkkijonon lopussa.
Sisällysluettelo
- Tarkista palindromi joka kerta - O(n^2) aika ja O(n) avaruus
- Knuth Morris Pratt -algoritmin käyttäminen - O(n) aika ja O(n) avaruus
Tarkista palindromi joka kerta - O(n^2) aika ja O(n) avaruus
C++Ratkaisu sisältää asteittain poistamalla merkkejä alku merkkijonosta yksitellen, kunnes merkkijonosta tulee a palindromi . Vastaus on poistettujen merkkien kokonaismäärä.
Harkitse esimerkiksi merkkijonoa s = 'täällä'. Tarkistamme ensin, onko koko merkkijono palindromi, mutta se ei ole. Seuraavaksi poistamme ensimmäisen merkin, joka johtaa merkkijono "kerätä". Tarkistamme uudelleen, mutta se ei silti ole palindromi. Poistamme sitten toisen merkin alusta jättää "ede". Tällä kertaa merkkijono on palindromi. Siksi lähtö on 2 edustaa alusta alkaen palindromin saavuttamiseksi poistettujen merkkien määrää.
// C++ code to find minimum number // of appends to make string Palindrome #include using namespace std; // Function to check if a given string is a palindrome bool isPalindrome(string s) { int left = 0 right = s.length() - 1; while (left < right) { if (s[left] != s[right]) return false; left++; right--; } return true; } // Function to find the minimum number of // characters to remove from the beginning int noOfAppends(string& s) { int n = s.length(); // Remove characters from the start until // the string becomes a palindrome for (int i = 0; i < n; i++) { if (isPalindrome(s.substr(i))) { // Return the number of characters removed return i; } } // If no palindrome is found remove // all but one character return n - 1; } int main() { string s = 'abede'; int result = noOfAppends(s); cout << result << endl; return 0; }
Java // Java code to find minimum number // of appends to make string Palindrome import java.util.*; class GfG { // Function to check if a given string is a palindrome static boolean isPalindrome(String s) { int left = 0 right = s.length() - 1; while (left < right) { if (s.charAt(left) != s.charAt(right)) return false; left++; right--; } return true; } // Function to find the minimum number of // characters to remove from the beginning static int noOfAppends(String s) { int n = s.length(); // Remove characters from the start until // the string becomes a palindrome for (int i = 0; i < n; i++) { if (isPalindrome(s.substring(i))) { // Return the number of characters removed return i; } } // If no palindrome is found remove // all but one character return n - 1; } public static void main(String[] args) { String s = 'abede'; int result = noOfAppends(s); System.out.println(result); } }
Python # Python code to find minimum number # of appends to make string Palindrome # Function to check if a given string is a palindrome def is_palindrome(s): left right = 0 len(s) - 1 while left < right: if s[left] != s[right]: return False left += 1 right -= 1 return True # Function to find the minimum number of # characters to remove from the beginning def no_of_appends(s): n = len(s) # Remove characters from the start until # the string becomes a palindrome for i in range(n): if is_palindrome(s[i:]): # Return the number of characters # removed return i # If no palindrome is found remove # all but one character return n - 1 if __name__ == '__main__': s = 'abede' result = no_of_appends(s) print(result)
C# // C# code to find minimum number // of appends to make string Palindrome using System; class GfG { // Function to check if a given string // is a palindrome static bool IsPalindrome(string s) { int left = 0 right = s.Length - 1; while (left < right) { if (s[left] != s[right]) return false; left++; right--; } return true; } // Function to find the minimum number of // characters to remove from the beginning static int NoOfAppends(string s) { int n = s.Length; // Remove characters from the start until // the string becomes a palindrome for (int i = 0; i < n; i++) { if (IsPalindrome(s.Substring(i))) { // Return the number of characters // removed return i; } } // If no palindrome is found remove all but // one character return n - 1; } static void Main(string[] args) { string s = 'abede'; int result = NoOfAppends(s); Console.WriteLine(result); } }
JavaScript // JavaScript code to find minimum number // of appends to make string Palindrome // Function to check if a given string is a palindrome function isPalindrome(s) { let left = 0 right = s.length - 1; while (left < right) { if (s[left] !== s[right]) return false; left++; right--; } return true; } // Function to find the minimum number of // characters to remove from the beginning function noOfAppends(s) { let n = s.length; // Remove characters from the start until // the string becomes a palindrome for (let i = 0; i < n; i++) { if (isPalindrome(s.substring(i))) { // Return the number of // characters removed return i; } } // If no palindrome is found remove // all but one character return n - 1; } const s = 'abede'; const result = noOfAppends(s); console.log(result);
Lähtö
2
Knuth Morris Pratt -algoritmin käyttäminen - O(n) aika ja O(n) avaruus
C++Lähestymistavan perusajatuksena on, että me laskea the suurin osamerkkijono lopusta ja langan pituus miinus tämä arvo on minimi liitteiden määrä. Logiikka on intuitiivinen, meidän ei tarvitse liittää palindromi ja vain ne, jotka eivät muodosta palindromia. Löytääksemme tämän suurimman palindromin lopusta me päinvastoin merkkijono laskea DFA.
The DFA (Deterministic Finite Automaton) yhteydessä mainittu Knuth Morris Pratt -algoritmi on käsite, jota käytetään auttamaan löytämään merkkijonon pisin etuliite, joka on myös jälkiliite ja käännä merkkijono uudelleen (saamalla takaisin alkuperäisen merkkijonon) ja etsi lopullinen tila, joka edustaa merkkijonon ja arvostetun merkkijonon osumien määrää, ja siten saamme suurimman alijonon, joka on palindromi lopusta.
// CPP program for the given approach // using 2D vector for DFA #include using namespace std; // Function to build the DFA and precompute the state vector<vector<int>> buildDFA(string& s) { int n = s.length(); // Number of possible characters (ASCII range) int c = 256; // Initialize 2D vector with zeros vector<vector<int>> dfa(n vector<int>(c 0)); int x = 0; dfa[0][s[0]] = 1; // Build the DFA for the given string for (int i = 1; i < n; i++) { for (int j = 0; j < c; j++) { dfa[i][j] = dfa[x][j]; } dfa[i][s[i]] = i + 1; x = dfa[x][s[i]]; } return dfa; } // Function to find the longest overlap // between the string and its reverse int longestOverlap(vector<vector<int>>& dfa string& query) { int ql = query.length(); int state = 0; // Traverse through the query to // find the longest overlap for (int i = 0; i < ql; i++) { state = dfa[state][query[i]]; } return state; } // Function to find the minimum // number of characters to append int minAppends(string s) { // Reverse the string string reversedS = s; reverse(reversedS.begin() reversedS.end()); // Build the DFA for the reversed string vector<vector<int>> dfa = buildDFA(reversedS); // Get the longest overlap with the original string int longestOverlapLength = longestOverlap(dfa s); // Minimum characters to append // to make the string a palindrome return s.length() - longestOverlapLength; } int main() { string s = 'abede'; cout << minAppends(s) << endl; return 0; }
Java // Java program for the given approach // using 2D array for DFA import java.util.*; class GfG { // Function to build the DFA and precompute the state static int[][] buildDFA(String s) { int n = s.length(); // Number of possible characters (ASCII range) int c = 256; // Initialize 2D array with zeros int[][] dfa = new int[n][c]; int x = 0; dfa[0][s.charAt(0)] = 1; // Build the DFA for the given string for (int i = 1; i < n; i++) { for (int j = 0; j < c; j++) { dfa[i][j] = dfa[x][j]; } dfa[i][s.charAt(i)] = i + 1; x = dfa[x][s.charAt(i)]; } return dfa; } // Function to find the longest overlap // between the string and its reverse static int longestOverlap(int[][] dfa String query) { int ql = query.length(); int state = 0; // Traverse through the query to // find the longest overlap for (int i = 0; i < ql; i++) { state = dfa[state][query.charAt(i)]; } return state; } // Function to find the minimum // number of characters to append static int minAppends(String s) { // Reverse the string String reversedS = new StringBuilder(s).reverse().toString(); // Build the DFA for the reversed string int[][] dfa = buildDFA(reversedS); // Get the longest overlap with the original string int longestOverlapLength = longestOverlap(dfa s); // Minimum characters to append // to make the string a palindrome return s.length() - longestOverlapLength; } public static void main(String[] args) { String s = 'abede'; System.out.println(minAppends(s)); } }
Python # Python program for the given approach # using 2D list for DFA # Function to build the DFA and precompute the state def buildDFA(s): n = len(s) # Number of possible characters (ASCII range) c = 256 # Initialize 2D list with zeros dfa = [[0] * c for _ in range(n)] x = 0 dfa[0][ord(s[0])] = 1 # Build the DFA for the given string for i in range(1 n): for j in range(c): dfa[i][j] = dfa[x][j] dfa[i][ord(s[i])] = i + 1 x = dfa[x][ord(s[i])] return dfa # Function to find the longest overlap # between the string and its reverse def longestOverlap(dfa query): ql = len(query) state = 0 # Traverse through the query to # find the longest overlap for i in range(ql): state = dfa[state][ord(query[i])] return state # Function to find the minimum # number of characters to append def minAppends(s): # Reverse the string reversedS = s[::-1] # Build the DFA for the reversed string dfa = buildDFA(reversedS) # Get the longest overlap with the # original string longestOverlapLength = longestOverlap(dfa s) # Minimum characters to append # to make the string a palindrome return len(s) - longestOverlapLength if __name__ == '__main__': s = 'abede' print(minAppends(s))
C# // C# program for the given approach // using 2D array for DFA using System; class GfG { // Function to build the DFA and precompute the state static int[] buildDFA(string s) { int n = s.Length; // Number of possible characters // (ASCII range) int c = 256; // Initialize 2D array with zeros int[] dfa = new int[n c]; int x = 0; dfa[0 s[0]] = 1; // Build the DFA for the given string for (int i = 1; i < n; i++) { for (int j = 0; j < c; j++) { dfa[i j] = dfa[x j]; } dfa[i s[i]] = i + 1; x = dfa[x s[i]]; } return dfa; } // Function to find the longest overlap // between the string and its reverse static int longestOverlap(int[] dfa string query) { int ql = query.Length; int state = 0; // Traverse through the query to // find the longest overlap for (int i = 0; i < ql; i++) { state = dfa[state query[i]]; } return state; } // Function to find the minimum // number of characters to append static int minAppends(string s) { // Reverse the string using char array char[] reversedArray = s.ToCharArray(); Array.Reverse(reversedArray); string reversedS = new string(reversedArray); // Build the DFA for the reversed string int[] dfa = buildDFA(reversedS); // Get the longest overlap with the original string int longestOverlapLength = longestOverlap(dfa s); // Minimum characters to append // to make the string a palindrome return s.Length - longestOverlapLength; } static void Main() { string s = 'abede'; Console.WriteLine(minAppends(s)); } }
JavaScript // JavaScript program for the given approach // using 2D array for DFA // Function to build the DFA and precompute the state function buildDFA(s) { let n = s.length; // Number of possible characters // (ASCII range) let c = 256; // Initialize 2D array with zeros let dfa = Array.from({ length: n } () => Array(c).fill(0)); let x = 0; dfa[0][s.charCodeAt(0)] = 1; // Build the DFA for the given string for (let i = 1; i < n; i++) { for (let j = 0; j < c; j++) { dfa[i][j] = dfa[x][j]; } dfa[i][s.charCodeAt(i)] = i + 1; x = dfa[x][s.charCodeAt(i)]; } return dfa; } // Function to find the longest overlap // between the string and its reverse function longestOverlap(dfa query) { let ql = query.length; let state = 0; // Traverse through the query to // find the longest overlap for (let i = 0; i < ql; i++) { state = dfa[state][query.charCodeAt(i)]; } return state; } // Function to find the minimum // number of characters to append function minAppends(s) { // Reverse the string let reversedS = s.split('').reverse().join(''); // Build the DFA for the reversed string let dfa = buildDFA(reversedS); // Get the longest overlap with the original string let longestOverlapLength = longestOverlap(dfa s); // Minimum characters to append // to make the string a palindrome return s.length - longestOverlapLength; } let s = 'abede'; console.log(minAppends(s));
Lähtö
2
Aiheeseen liittyvä artikkeli:
- Dynaaminen ohjelmointi | Sarja 28 (minimilisäyksiä palindromin muodostamiseksi)