135 lines
2.6 KiB
Go
135 lines
2.6 KiB
Go
package top100liked
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import (
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"fmt"
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"testing"
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)
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// https://leetcode.cn/problems/find-median-from-data-stream/?envType=study-plan-v2&envId=top-100-liked
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type heap[T any] struct {
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data []T
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compareFunc func(T, T) bool
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}
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func NewHeap[T any](compareFunc func(T, T) bool) heap[T] {
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return heap[T]{
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compareFunc: compareFunc,
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}
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}
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func (h *heap[T]) Up(idx int) {
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for (idx-1)/2 >= 0 {
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cur := h.data[idx]
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p := h.data[(idx-1)/2]
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if h.compareFunc(cur, p) {
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h.data[idx], h.data[(idx-1)/2] = h.data[(idx-1)/2], h.data[idx]
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idx = (idx - 1) / 2
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} else {
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break
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}
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}
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}
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func (h *heap[T]) Down(idx int) {
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for {
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l, r := 2*idx+1, 2*idx+2
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m := idx
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if l < len(h.data) && h.compareFunc(h.data[l], h.data[m]) {
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m = l
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}
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if r < len(h.data) && h.compareFunc(h.data[r], h.data[m]) {
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m = r
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}
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if m == idx {
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break
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}
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h.data[idx], h.data[m] = h.data[m], h.data[idx]
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idx = m
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}
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}
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func (h *heap[T]) Push(val T) {
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h.data = append(h.data, val)
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h.Up(len(h.data) - 1)
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}
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func (h *heap[T]) Pop() T {
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if len(h.data) <= 0 {
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var zero T
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return zero
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}
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old := h.data[0]
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h.data[0] = h.data[len(h.data)-1]
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h.data = h.data[:len(h.data)-1]
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h.Down(0)
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return old
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}
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func (h *heap[T]) Top() T {
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if len(h.data) > 0 {
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return h.data[0]
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}
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var zero T
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return zero
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}
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func (h *heap[T]) Len() int {
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return len(h.data)
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}
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type MedianFinder struct {
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left heap[int] // 小
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right heap[int] // 大
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}
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func Constructor() MedianFinder {
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return MedianFinder{
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left: NewHeap(func(i1, i2 int) bool { return i1 > i2 }),
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right: NewHeap(func(i1, i2 int) bool { return i1 < i2 }),
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}
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}
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func (this *MedianFinder) AddNum(num int) {
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if this.left.Len() == 0 {
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this.left.Push(num)
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return
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}
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if num >= this.left.Top() {
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this.right.Push(num)
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} else {
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this.left.Push(num)
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}
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if this.left.Len() > this.right.Len()+1 {
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v := this.left.Pop()
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this.right.Push(v)
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}
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if this.right.Len() > this.left.Len()+1 {
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v := this.right.Pop()
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this.left.Push(v)
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}
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}
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func (this *MedianFinder) FindMedian() float64 {
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switch (this.left.Len() + this.right.Len()) % 2 {
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case 0:
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return (float64(this.left.Top()) + float64(this.right.Top())) / 2
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case 1:
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if this.left.Len() > this.right.Len() {
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return float64(this.left.Top())
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} else {
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return float64(this.right.Top())
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}
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}
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return 0
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}
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func Test(t *testing.T) {
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medianFinder := Constructor()
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medianFinder.AddNum(1) // arr = [1]
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medianFinder.AddNum(2) // arr = [1, 2]
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fmt.Println(medianFinder.FindMedian()) // 返回 1.5 ((1 + 2) / 2)
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medianFinder.AddNum(3) // arr[1, 2, 3]
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fmt.Println(medianFinder.FindMedian()) // return 2.0
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}
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