靈機一動　

◎ 靈機一動 língjī-yīdòng

[bright idea occurs;be seized by a sudden impulse;have a brainwave; flash through one‘s mind; when the maggot bites] 突然想出個好辦法

他靈機一動,撒了一個謊。——周立波《暴風驟雨》