beat (/cudgel/rack)one’s brains; in a painstaking effort; spare no pains(/efforts); take great (/a lot of) pains (/trouble); with much ado; with painful care; lay oneself out; leave on stone unturned
❍ 敌人在～地研究对策。(杨植霖《王若飞在狱中》66) They racked their brains to try and find methods to handle him.
❍ 同学们，老王麻子的剪刀有真有假，考古学家也常为出土文物的真伪而～。(杨沫《青春之歌》561) Fellow students!Things aren’t always what they seem to be! Even the archaeologists have a hard time deciding which relics dug out of the earth are genuine and which are faked.
❍ 象你这样～，都是徒劳！(杨植霖《王若飞在狱中》24) You’ve taken great pains for nothing!
煞费苦心
rack (or cudgel) one’s brains;take great pains;make painstaking efforts
他们为了攻克技术难关，真是～。They took great pains to solve technical problems./～地研究对策rack one’s brains to work out countermeasures
煞费苦心shà fèi kǔ xīn
煞：很、极。形容费尽了心思。take great pains, at great pains, with much ado, with great pains, beat one’s brains