css - How to use flex to implement a three-column layout, but the height of the child elements must be adaptive?

Question

I want to use flex to implement the three-column layout in the picture. I currently encounter the following problems:

When the parent element sets display: flex, the height of the three columns is the same, and I want the height of the three columns to be the same. The height is adaptive. I tried setting flex-direction:colume and flex-flow:row nowrap but couldn't achieve the desired effect. Does anyone know how to set it?

我想大声告诉你 · Answer

It’s very simple
If you don’t consider line breaks
demo1