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135 lines
2.9 KiB
135 lines
2.9 KiB
// 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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/* 链式地址哈希表 */
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type hashMapChaining struct {
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size int // 键值对数量
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capacity int // 哈希表容量
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loadThres float64 // 触发扩容的负载因子阈值
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extendRatio int // 扩容倍数
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buckets [][]pair // 桶数组
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}
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/* 构造方法 */
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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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/* 哈希函数 */
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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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/* 负载因子 */
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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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/* 查询操作 */
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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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// 遍历桶，若找到 key ，则返回对应 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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// 若未找到 key ，则返回空字符串
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return ""
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}
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/* 添加操作 */
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func (m *hashMapChaining) put(key int, val string) {
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// 当负载因子超过阈值时，执行扩容
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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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// 遍历桶，若遇到指定 key ，则更新对应 val 并返回
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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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// 若无该 key ，则将键值对添加至尾部
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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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/* 删除操作 */
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func (m *hashMapChaining) remove(key int) {
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idx := m.hashFunc(key)
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// 遍历桶，从中删除键值对
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for i, p := range m.buckets[idx] {
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if p.key == key {
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// 切片删除
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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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/* 扩容哈希表 */
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func (m *hashMapChaining) extend() {
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// 暂存原哈希表
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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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// 初始化扩容后的新哈希表
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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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// 将键值对从原哈希表搬运至新哈希表
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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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/* 打印哈希表 */
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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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