mirror of
https://github.com/krahets/hello-algo.git
synced 2024-12-26 01:46:27 +08:00
158 lines
4.1 KiB
Kotlin
158 lines
4.1 KiB
Kotlin
|
/**
|
|||
|
* File: my_heap.kt
|
|||
|
* Created Time: 2024-01-25
|
|||
|
* Author: curtishd (1023632660@qq.com)
|
|||
|
*/
|
|||
|
|
|||
|
package chapter_heap
|
|||
|
|
|||
|
import utils.printHeap
|
|||
|
import java.util.*
|
|||
|
|
|||
|
/* 大頂堆積 */
|
|||
|
class MaxHeap(nums: List<Int>?) {
|
|||
|
// 使用串列而非陣列,這樣無須考慮擴容問題
|
|||
|
// 將串列元素原封不動新增進堆積
|
|||
|
private val maxHeap = ArrayList(nums!!)
|
|||
|
|
|||
|
/* 建構子,根據輸入串列建堆積 */
|
|||
|
init {
|
|||
|
// 堆積化除葉節點以外的其他所有節點
|
|||
|
for (i in parent(size() - 1) downTo 0) {
|
|||
|
siftDown(i)
|
|||
|
}
|
|||
|
}
|
|||
|
|
|||
|
/* 獲取左子節點的索引 */
|
|||
|
private fun left(i: Int): Int {
|
|||
|
return 2 * i + 1
|
|||
|
}
|
|||
|
|
|||
|
/* 獲取右子節點的索引 */
|
|||
|
private fun right(i: Int): Int {
|
|||
|
return 2 * i + 2
|
|||
|
}
|
|||
|
|
|||
|
/* 獲取父節點的索引 */
|
|||
|
private fun parent(i: Int): Int {
|
|||
|
return (i - 1) / 2 // 向下整除
|
|||
|
}
|
|||
|
|
|||
|
/* 交換元素 */
|
|||
|
private fun swap(i: Int, j: Int) {
|
|||
|
maxHeap[i] = maxHeap[j].also { maxHeap[j] = maxHeap[i] }
|
|||
|
}
|
|||
|
|
|||
|
/* 獲取堆積大小 */
|
|||
|
fun size(): Int {
|
|||
|
return maxHeap.size
|
|||
|
}
|
|||
|
|
|||
|
/* 判斷堆積是否為空 */
|
|||
|
fun isEmpty(): Boolean {
|
|||
|
/* 判斷堆積是否為空 */
|
|||
|
return size() == 0
|
|||
|
}
|
|||
|
|
|||
|
/* 訪問堆積頂元素 */
|
|||
|
fun peek(): Int {
|
|||
|
return maxHeap[0]
|
|||
|
}
|
|||
|
|
|||
|
/* 元素入堆積 */
|
|||
|
fun push(value: Int) {
|
|||
|
// 新增節點
|
|||
|
maxHeap.add(value)
|
|||
|
// 從底至頂堆積化
|
|||
|
siftUp(size() - 1)
|
|||
|
}
|
|||
|
|
|||
|
/* 從節點 i 開始,從底至頂堆積化 */
|
|||
|
private fun siftUp(it: Int) {
|
|||
|
// Kotlin的函式參數不可變,因此建立臨時變數
|
|||
|
var i = it
|
|||
|
while (true) {
|
|||
|
// 獲取節點 i 的父節點
|
|||
|
val p = parent(i)
|
|||
|
// 當“越過根節點”或“節點無須修復”時,結束堆積化
|
|||
|
if (p < 0 || maxHeap[i] <= maxHeap[p]) break
|
|||
|
// 交換兩節點
|
|||
|
swap(i, p)
|
|||
|
// 迴圈向上堆積化
|
|||
|
i = p
|
|||
|
}
|
|||
|
}
|
|||
|
|
|||
|
/* 元素出堆積 */
|
|||
|
fun pop(): Int {
|
|||
|
// 判空處理
|
|||
|
if (isEmpty()) throw IndexOutOfBoundsException()
|
|||
|
// 交換根節點與最右葉節點(交換首元素與尾元素)
|
|||
|
swap(0, size() - 1)
|
|||
|
// 刪除節點
|
|||
|
val value = maxHeap.removeAt(size() - 1)
|
|||
|
// 從頂至底堆積化
|
|||
|
siftDown(0)
|
|||
|
// 返回堆積頂元素
|
|||
|
return value
|
|||
|
}
|
|||
|
|
|||
|
/* 從節點 i 開始,從頂至底堆積化 */
|
|||
|
private fun siftDown(it: Int) {
|
|||
|
// Kotlin的函式參數不可變,因此建立臨時變數
|
|||
|
var i = it
|
|||
|
while (true) {
|
|||
|
// 判斷節點 i, l, r 中值最大的節點,記為 ma
|
|||
|
val l = left(i)
|
|||
|
val r = right(i)
|
|||
|
var ma = i
|
|||
|
if (l < size() && maxHeap[l] > maxHeap[ma]) ma = l
|
|||
|
if (r < size() && maxHeap[r] > maxHeap[ma]) ma = r
|
|||
|
// 若節點 i 最大或索引 l, r 越界,則無須繼續堆積化,跳出
|
|||
|
if (ma == i) break
|
|||
|
// 交換兩節點
|
|||
|
swap(i, ma)
|
|||
|
// 迴圈向下堆積化
|
|||
|
i = ma
|
|||
|
}
|
|||
|
}
|
|||
|
|
|||
|
/* 列印堆積(二元樹) */
|
|||
|
fun print() {
|
|||
|
val queue = PriorityQueue { a: Int, b: Int -> b - a }
|
|||
|
queue.addAll(maxHeap)
|
|||
|
printHeap(queue)
|
|||
|
}
|
|||
|
}
|
|||
|
|
|||
|
/* Driver Code */
|
|||
|
fun main() {
|
|||
|
/* 初始化大頂堆積 */
|
|||
|
val maxHeap = MaxHeap(mutableListOf(9, 8, 6, 6, 7, 5, 2, 1, 4, 3, 6, 2))
|
|||
|
println("\n輸入串列並建堆積後")
|
|||
|
maxHeap.print()
|
|||
|
|
|||
|
/* 獲取堆積頂元素 */
|
|||
|
var peek = maxHeap.peek()
|
|||
|
print("\n堆積頂元素為 $peek\n")
|
|||
|
|
|||
|
/* 元素入堆積 */
|
|||
|
val value = 7
|
|||
|
maxHeap.push(value)
|
|||
|
print("\n元素 $value 入堆積後\n")
|
|||
|
maxHeap.print()
|
|||
|
|
|||
|
/* 堆積頂元素出堆積 */
|
|||
|
peek = maxHeap.pop()
|
|||
|
print("\n堆積頂元素 $peek 出堆積後\n")
|
|||
|
maxHeap.print()
|
|||
|
|
|||
|
/* 獲取堆積大小 */
|
|||
|
val size = maxHeap.size()
|
|||
|
print("\n堆積元素數量為 $size\n")
|
|||
|
|
|||
|
/* 判斷堆積是否為空 */
|
|||
|
val isEmpty = maxHeap.isEmpty()
|
|||
|
print("\n堆積是否為空 $isEmpty\n")
|
|||
|
}
|