How to delete all my pictures on my iphone 5 without a computer?

I'm running on the latest update

Open photo app--> click select(on the top and on the right)-->in each part there's a select button--> click it--> you will see that all the pics in this part are selected and repeat it for all of the other parts and click the delete button but you can't do it on years or collections only on moments

hope you like it