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68 lines (56 loc) · 1.54 KB
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import java.util.HashMap;
import java.util.Map;
public class AnagramDetection {
private Map<Character, Integer> charToPrimeMap;
public AnagramDetection() {
charToPrimeMap = new HashMap<Character, Integer>();
populateCharToPrimeMap();
}
private boolean isPrime(int n) {
for (int i = 2; i < Math.ceil(Math.sqrt(n)); ++i) {
if (n % i == 0) {
return false;
}
}
return true;
}
private int getNthPrime(int n) {
int nthPrime = 2;
while(n > 0) {
if (isPrime(nthPrime)) {
--n;
}
++nthPrime;
}
return nthPrime;
}
private void populateCharToPrimeMap() {
for (int i = 0; i < 52; i += 2) {
charToPrimeMap.put((char)('a'+i/2), getNthPrime(i/2));
charToPrimeMap.put(Character.toUpperCase((char)('a'+i/2)), getNthPrime(i/2+1));
}
}
private int hashString(String input) {
int hash = 1;
for (char c: input.toCharArray()) {
hash *= charToPrimeMap.get(c);
}
return hash;
}
public int detectAnagrams(String original, String anagram) {
char[] originalChars = original.toCharArray();
int anagramCount = 0;
for (int i = 0; i < original.length() - anagram.length(); ++i) {
String currentSubstring = String.copyValueOf(originalChars, i, anagram.length());
if (hashString(currentSubstring) == hashString(anagram)) {
++anagramCount;
}
}
return anagramCount;
}
public static void main(String[] args) {
AnagramDetection a = new AnagramDetection();
System.out.println(a.detectAnagrams("AdnBndAndBdaBn", "dAn"));
System.out.println(a.detectAnagrams("AbrAcadAbRa", "cAda"));
}
}