瞎猫碰上死耗子 (xiā māo pèng shàng sǐ hào zi)

瞎猫碰上死耗子

(xiā māo pèng shàng sǐ hào zi)
English Translation:“A blind cat meets a dead mouse.”

Meaning:
The closest English equivalent would be “to take a shot in the dark.” You may do something without much confidence, but still succeed.

Example:
我没想到能赢，真是瞎猫碰上死耗子。
(I didn’t expect to win; it was truly “a blind cat meets a dead mouse.”)

Source: Hello Mandarin