135 lines
3.1 KiB
Go
135 lines
3.1 KiB
Go
// File: hash_map_chaining.go
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// Created Time: 2023-06-23
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// Author: Reanon (793584285@qq.com)
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package chapter_hashing
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import (
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"fmt"
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"strconv"
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"strings"
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)
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/* Chained address hash table */
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type hashMapChaining struct {
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size int // Number of key-value pairs
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capacity int // Hash table capacity
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loadThres float64 // Load factor threshold for triggering expansion
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extendRatio int // Expansion multiplier
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buckets [][]pair // Bucket array
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}
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/* Constructor */
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func newHashMapChaining() *hashMapChaining {
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buckets := make([][]pair, 4)
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for i := 0; i < 4; i++ {
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buckets[i] = make([]pair, 0)
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}
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return &hashMapChaining{
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size: 0,
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capacity: 4,
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loadThres: 2.0 / 3.0,
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extendRatio: 2,
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buckets: buckets,
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}
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}
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/* Hash function */
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func (m *hashMapChaining) hashFunc(key int) int {
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return key % m.capacity
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}
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/* Load factor */
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func (m *hashMapChaining) loadFactor() float64 {
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return float64(m.size) / float64(m.capacity)
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}
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/* Query operation */
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func (m *hashMapChaining) get(key int) string {
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idx := m.hashFunc(key)
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bucket := m.buckets[idx]
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// Traverse the bucket, if the key is found, return the corresponding val
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for _, p := range bucket {
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if p.key == key {
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return p.val
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}
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}
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// If key not found, return an empty string
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return ""
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}
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/* Add operation */
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func (m *hashMapChaining) put(key int, val string) {
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// When the load factor exceeds the threshold, perform expansion
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if m.loadFactor() > m.loadThres {
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m.extend()
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}
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idx := m.hashFunc(key)
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// Traverse the bucket, if the specified key is encountered, update the corresponding val and return
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for i := range m.buckets[idx] {
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if m.buckets[idx][i].key == key {
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m.buckets[idx][i].val = val
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return
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}
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}
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// If the key is not found, add the key-value pair to the end
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p := pair{
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key: key,
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val: val,
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}
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m.buckets[idx] = append(m.buckets[idx], p)
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m.size += 1
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}
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/* Remove operation */
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func (m *hashMapChaining) remove(key int) {
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idx := m.hashFunc(key)
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// Traverse the bucket, remove the key-value pair from it
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for i, p := range m.buckets[idx] {
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if p.key == key {
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// Slice removal
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m.buckets[idx] = append(m.buckets[idx][:i], m.buckets[idx][i+1:]...)
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m.size -= 1
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break
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}
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}
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}
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/* Extend hash table */
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func (m *hashMapChaining) extend() {
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// Temporarily store the original hash table
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tmpBuckets := make([][]pair, len(m.buckets))
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for i := 0; i < len(m.buckets); i++ {
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tmpBuckets[i] = make([]pair, len(m.buckets[i]))
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copy(tmpBuckets[i], m.buckets[i])
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}
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// Initialize the extended new hash table
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m.capacity *= m.extendRatio
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m.buckets = make([][]pair, m.capacity)
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for i := 0; i < m.capacity; i++ {
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m.buckets[i] = make([]pair, 0)
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}
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m.size = 0
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// Move key-value pairs from the original hash table to the new hash table
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for _, bucket := range tmpBuckets {
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for _, p := range bucket {
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m.put(p.key, p.val)
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}
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}
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}
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/* Print hash table */
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func (m *hashMapChaining) print() {
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var builder strings.Builder
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for _, bucket := range m.buckets {
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builder.WriteString("[")
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for _, p := range bucket {
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builder.WriteString(strconv.Itoa(p.key) + " -> " + p.val + " ")
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}
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builder.WriteString("]")
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fmt.Println(builder.String())
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builder.Reset()
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}
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}
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