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HashTableDynamic.java
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101 lines (82 loc) · 2.38 KB
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import java.util.TreeMap;
public class HashTableDynamic<K, V> {
// 链地址法
private static final int upperTol = 10;
private static final int lowerTol = 2;
private static final int initCapacity = 7;
private TreeMap<K, V>[] hashTable;
private int M;
private int size;
public HashTableDynamic(int M) {
this.M = M;
size = 0;
hashTable = new TreeMap[M];
for (int i = 0; i < M; i++) {
hashTable[i] = new TreeMap<>();
}
}
public HashTableDynamic() {
this(initCapacity);
}
private int hash(K key) {
return (key.hashCode() & 0x7fffffff) % M;
}
public int getSize() {
return size;
}
public void add(K key, V value) {
TreeMap<K, V> map = hashTable[hash(key)];
if (map.containsKey(key)) {
map.put(key, value);
} else {
map.put(key, value);
size++;
if (size >= upperTol * M) {
resize(2 * M);
}
}
}
public V remove(K key) {
TreeMap<K, V> map = hashTable[hash(key)];
V ret = null;
if (map.containsKey(key)) {
ret = map.remove(key);
size--;
// if (size< lowerTol * M&&M/2>0){
if (size < lowerTol * M && M / 2 >= initCapacity) {
resize(M / 2);
}
}
return ret;
}
public void set(K key, V value) {
TreeMap<K, V> map = hashTable[hash(key)];
if (!map.containsKey(key)) {
throw new IllegalArgumentException(key + " doesn't exist!");
}
map.put(key, value);
}
public boolean contains(K key) {
return hashTable[hash(key)].containsKey(key);
}
public V get(K key) {
return hashTable[hash(key)].get(key);
}
private void resize(int newM) {
TreeMap<K, V>[] newHashTable = new TreeMap[newM];
for (int i = 0; i < newM; i++) {
newHashTable[i] = new TreeMap<>();
}
// 注意，M的变化
int oldM = M;
this.M = newM;
for (int i = 0; i < oldM; i++) {
TreeMap<K, V> map = hashTable[i];
for (K key : map.keySet()) {
// hash(key) M的变化
newHashTable[hash(key)].put(key, map.get(key));
}
}
this.hashTable = newHashTable;
}
}