find median from data stream solution

Author: yhkee0404

find-median-from-data-stream/yhkee0404.go

@@ -0,0 +1,52 @@
+type MedianFinder struct {
+    lq Heap
+    rq Heap
+}
+
+type Heap []int // S(n) = O(n)
+
+func (pq Heap) Len() int {return len(pq)}
+func (pq Heap) Less(i, j int) bool {return pq[i] < pq[j]}
+func (pq Heap) Swap(i, j int) {pq[i], pq[j] = pq[j], pq[i]}
+func (pq *Heap) Push(x any) {*pq = append(*pq, x.(int))}
+func (pq *Heap) Pop() any {
+    x := (*pq)[len(*pq) - 1]
+    *pq = (*pq)[: len(*pq) - 1]
+    return x
+}
+
+
+func Constructor() MedianFinder {
+    return MedianFinder{}
+}
+
+
+func (this *MedianFinder) AddNum(num int)  { // T(n) = O(logn)
+    if len(this.rq) != 0 && this.rq[0] <= num {
+        heap.Push(&this.rq, num)
+        if len(this.lq) == len(this.rq) - 1 {
+            heap.Push(&this.lq, - heap.Pop(&this.rq).(int))
+        }
+        return
+    }
+    heap.Push(&this.lq, - num)
+    if len(this.lq) == len(this.rq) + 2 {
+        heap.Push(&this.rq, - heap.Pop(&this.lq).(int))
+    }
+}
+
+
+func (this *MedianFinder) FindMedian() float64 { // T(n) = O(1)
+    if len(this.lq) > len(this.rq) {
+        return float64(- this.lq[0])
+    }
+    return float64(- this.lq[0] + this.rq[0]) / 2
+}
+
+
+/**
+ * Your MedianFinder object will be instantiated and called as such:
+ * obj := Constructor();
+ * obj.AddNum(num);
+ * param_2 := obj.FindMedian();
+ */