题目描述
Farmer John has arranged his N (1 ≤ N ≤ 5,000) cows in a row and many of them are facing forward, like good cows. Some of them are facing backward, though, and he needs them all to face fo...
Mongo DB Study: first face with mongo DB
1. study methods:
1. Translate: I am the mongo DB organization website truck man. And I may use my knowledge to help myself learn more.
2. ...