S obzirom na a niz s zadatak je pronaći minimum likovi koji će biti pridodano (umetanje na kraju) napraviti niz palindroma.
Primjeri:
Ulazni : s = 'gotovo'
Izlaz : 2
Obrazloženje: Možemo napraviti string palindrom kao 'abede ne ' dodavanjem ne na kraju niza.
Ulazni :s = 'aabb'
Izlaz : 2
Obrazloženje: Možemo napraviti string palindrom kao 'aabb aa ' dodavanjem aa na kraju niza.
Sadržaj
- Provjerite palindrom svaki put - O(n^2) vremena i O(n) prostora
- Korištenje Knuth Morris Pratt algoritma - O(n) vremena i O(n) prostora
Provjerite palindrom svaki put - O(n^2) vremena i O(n) prostora
C++Rješenje uključuje postupno uklanjanje znakova iz početak niza jedan po jedan dok niz ne postane a palindrom . Odgovor će biti ukupan broj uklonjenih znakova.
Na primjer, razmotrite niz s = 'ovdje'. Prvo provjeravamo je li cijeli niz palindrom, što nije. Zatim uklanjamo prvi znak što rezultira string 'prositi'. Ponovno provjeravamo, ali još uvijek nije palindrom. Zatim uklanjamo još jedan znak od početka ostavljajući 'ede'. Ovaj put niz je palindrom. Stoga je izlaz je 2 predstavlja broj znakova uklonjenih od početka da bi se postigao palindrom.
// 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);
Izlaz
2
Korištenje Knuth Morris Pratt algoritma - O(n) vremena i O(n) prostora
C++Osnovna ideja pristupa je da mi izračunati the najveći podniz s kraja i duljina niza minus ova vrijednost je minimum broj dodavanja. Logika je intuitivna, ne moramo dodavati palindrom i to samo one koje ne čine palindrom. Da pronađemo ovaj najveći palindrom s kraja mi obrnuti string izračunati DFA.
The DFA (Deterministički konačni automat) spomenuto u kontekstu Knuth Morris Pratt algoritam je koncept koji se koristi za pronalaženje najduži prefiks niza koji je ujedno i sufiks i ponovno preokrenuti niz (dobivši tako natrag originalni niz) i pronaći konačno stanje koje predstavlja broj podudaranja niza s poštovanim nizom i stoga dobivamo najveći podniz koji je palindrom od kraja.
// 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));
Izlaz
2
Povezani članak:
- Dinamičko programiranje | Skup 28 (Minimalni broj umetanja za formiranje palindroma)