Two Heaps Visualization

Elements: $[1, 2, 3, 4, 5]$

Max-heap (smaller half): $[1, 2, 3]$, root = $3$

Min-heap (larger half): $[4, 5]$, root = $4$

Median: with $5$ elements, max-heap is larger. Its root ($3$) is the median.

If you add $6$: Max-heap: $[3, 2, 1]$, root = $3$

Min-heap: $[4, 5, 6]$, root = $4$

Median: average of roots = $(3 + 4) / 2 = 3.5$.