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Copy pathQuadraticProbingHashTable.java
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164 lines (127 loc) · 3.54 KB
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package ch05;
/**
* Created by cookfront on 2017/3/14.
*/
public class QuadraticProbingHashTable<AnyType> {
private static class HashEntry<AnyType> {
public AnyType element;
public boolean isActive;
public HashEntry(AnyType e) {
this(e, true);
}
public HashEntry(AnyType e, boolean active) {
element = e;
isActive = active;
}
}
private static final int DEFAULT_TABLE_SIZE = 101;
private HashEntry<AnyType> [] array;
private int theSize;
private int occupied;
public QuadraticProbingHashTable() {
this(DEFAULT_TABLE_SIZE);
}
public QuadraticProbingHashTable(int size) {
allocateArray(size);
makeEmpty();
}
public boolean insert(AnyType x) {
int currentPos = findPos(x);
if (isActive(currentPos)) {
return false;
}
if (array[currentPos] == null) {
++occupied;
}
array[currentPos] = new HashEntry<AnyType>(x, true);
++theSize;
if (occupied > array.length / 2) {
rehash();
}
return true;
}
private void rehash() {
HashEntry<AnyType> [] oldArray = array;
// Create a new double-sized, empty table
allocateArray(2 * oldArray.length);
occupied = 0;
theSize = 0;
// Copy table over
for (HashEntry<AnyType> entry : oldArray)
if (entry != null && entry.isActive)
insert(entry.element);
}
public void makeEmpty() {
doClear();
}
private void doClear() {
theSize = 0;
for (int i = 0; i < array.length; i++) {
array[i] = null;
}
}
private int myhash(AnyType x) {
int hashVal = x.hashCode();
hashVal %= array.length;
if (hashVal < 0)
hashVal += array.length;
return hashVal;
}
private void allocateArray(int arraySize) {
array = new HashEntry[nextPrime(arraySize)];
}
public boolean contains(AnyType x) {
int currentPos = findPos(x);
return isActive(currentPos);
}
private int findPos(AnyType x) {
int offset = 1;
int currentPos = myhash(x);
while(array[currentPos] != null && !array[currentPos].element.equals(x)) {
currentPos += offset;
offset += 2;
if (currentPos >= array.length) {
currentPos -= array.length;
}
}
return currentPos;
}
public boolean remove(AnyType x) {
int currentPos = findPos(x);
if (isActive(currentPos)) {
array[ currentPos ].isActive = false;
theSize--;
return true;
} else
return false;
}
public int size() {
return theSize;
}
public int capacity() {
return array.length;
}
private boolean isActive(int currentPos) {
return array[currentPos] != null && array[currentPos].isActive;
}
private static int nextPrime(int n) {
if (n % 2 == 0)
n++;
for (; !isPrime( n ); n += 2)
;
return n;
}
private static boolean isPrime(int n) {
if (n == 2 || n == 3)
return true;
if (n == 1 || n % 2 == 0)
return false;
for (int i = 3; i * i <= n; i += 2)
if (n % i == 0)
return false;
return true;
}
public static void main(String ...args) {
System.out.println("test");
}
}