Given a two$-$dimensional inter matrix, $0$ represents air and $1$ represents cargo. Use the lowest row as ground to find the column where cargo is hanging.

$[000]$

$[111]$

$[101]$

output is $[1]1$ means there is a dangling item in the $1$st column

Followup: If the goods are sticky, they will stick to the goods above, below,

left, and right and will not fall down.