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BloomFilters.java
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103 lines (101 loc) · 2.39 KB
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package interview.algorithm;
/**
* 自己实现一个布隆过滤
*/
public class BloomFilters {
/**
* 数组长度
*/
private int arraySize;
/**
* 数组
*/
private int[] array;
public BloomFilters(int arraySize) {
this.arraySize = arraySize;
array = new int[arraySize];
}
/**
* 写入数据
* @param key
*/
public void add(String key) {
int first = hashcode_1(key);
int second = hashcode_2(key);
int third = hashcode_3(key);
array[first % arraySize] = 1;
array[second % arraySize] = 1;
array[third % arraySize] = 1;
}
/**
* 判断数据是否存在
* @param key
* @return
*/
public boolean check(String key) {
int first = hashcode_1(key);
int second = hashcode_2(key);
int third = hashcode_3(key);
int firstIndex = array[first % arraySize];
if (firstIndex == 0) {
return false;
}
int secondIndex = array[second % arraySize];
if (secondIndex == 0) {
return false;
}
int thirdIndex = array[third % arraySize];
if (thirdIndex == 0) {
return false;
}
return true;
}
/**
* hash 算法1
* @param key
* @return
*/
private int hashcode_1(String key) {
int hash = 0;
int i;
for (i = 0; i < key.length(); ++i) {
hash = 33 * hash + key.charAt(i);
}
return Math.abs(hash);
}
/**
* hash 算法2
* @param data
* @return
*/
private int hashcode_2(String data) {
final int p = 16777619;
int hash = (int) 2166136261L;
for (int i = 0; i < data.length(); i++) {
hash = (hash ^ data.charAt(i)) * p;
}
hash += hash << 13;
hash ^= hash >> 7;
hash += hash << 3;
hash ^= hash >> 17;
hash += hash << 5;
return Math.abs(hash);
}
/**
* hash 算法3
* @param key
* @return
*/
private int hashcode_3(String key) {
int hash, i;
for (hash = 0, i = 0; i < key.length(); ++i) {
hash += key.charAt(i);
hash += (hash << 10);
hash ^= (hash >> 6);
}
hash += (hash << 3);
hash ^= (hash >> 11);
hash += (hash << 15);
return Math.abs(hash);
}
}