feat: wednesday

pkg/find_median_from_data_stream/main.go

@@ -0,0 +1,82 @@
+package findmedianfromdatastream
+
+import "container/heap"
+
+type IntHeap []int
+
+func (h IntHeap) Len() int           { return len(h) }
+func (h IntHeap) Less(i, j int) bool { return h[i] < h[j] }
+func (h IntHeap) Swap(i, j int)      { h[i], h[j] = h[j], h[i] }
+
+func (h *IntHeap) Push(x any) {
+	*h = append(*h, x.(int))
+}
+
+func (h IntHeap) Peek() int {
+	return h[0]
+}
+
+func (h *IntHeap) Pop() any {
+	old := *h
+	x := old[len(old)-1]
+	*h = old[:len(old)-1]
+	return x
+}
+
+type MedianFinder struct {
+	// Positive min-heap of top half of values.
+	top *IntHeap
+	// Negative min-heap of bottom half of values.
+	bottom *IntHeap
+}
+
+func Constructor() MedianFinder {
+	result := MedianFinder{
+		top:    &IntHeap{},
+		bottom: &IntHeap{},
+	}
+
+	heap.Init(result.top)
+	heap.Init(result.bottom)
+	return result
+}
+
+func (m *MedianFinder) AddNum(num int) {
+	if m.bottom.Len() > m.top.Len() {
+		if -m.bottom.Peek() <= num {
+			heap.Push(m.top, num)
+		} else {
+			val := heap.Pop(m.bottom).(int)
+			heap.Push(m.top, -val)
+			heap.Push(m.bottom, -num)
+		}
+	} else if m.bottom.Len() < m.top.Len() {
+		if m.top.Peek() >= num {
+			heap.Push(m.bottom, -num)
+		} else {
+			val := heap.Pop(m.top).(int)
+			heap.Push(m.bottom, -val)
+			heap.Push(m.top, num)
+		}
+	} else {
+		if m.top.Len() == 0 {
+			heap.Push(m.top, num)
+		} else {
+			if median := m.FindMedian(); float64(num) > median {
+				heap.Push(m.top, num)
+			} else {
+				heap.Push(m.bottom, -num)
+			}
+		}
+	}
+}
+
+func (m *MedianFinder) FindMedian() float64 {
+	if m.bottom.Len() > m.top.Len() {
+		return float64(-m.bottom.Peek())
+	} else if m.bottom.Len() < m.top.Len() {
+		return float64(m.top.Peek())
+	} else {
+		return float64(m.top.Peek()-m.bottom.Peek()) / 2.0
+	}
+}