Revert "Removed extraneous algorithm include"
Revert "Removed extraneous algorithm include"

This reverts commit 9c58974abeac828196515343d6d7836bfd041b12.

stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/math