Star!
Snap the flamingo is taking a class photo. Line the animal friends up, shortest on the left and tallest on the right. You can only swap two friends who stand right next to each other: tap the swap button between them, or drag one friend onto its neighbour. Swapping a pair that is already in order just costs a swap.
Stuck? Tap Help me and the first pair in the wrong order glows. Finish in the fewest swaps for a star. When the photo is taken Snap shows you the trick you just used, called Bubble Sort: look at two neighbours, swap them if the left one is taller, and go along the row again and again. Every finished photo adds a friend to your album.