9.12 - medium - 281:320

练手题：
576. Out of Boundary Paths
583. Delete Operation for Two Strings
592. Fraction Addition and Subtraction: 好麻烦的一题
609. Find Duplicate File in System
611. Valid Triangle Number
616. Add Bold Tag in String
634. Find the Derangement of An Array
621. Task Scheduler
625. Minimum Factorization
638. Shopping Offers
636. Exclusive Time of Functions
658. Find K Closest Elements
649. Dota2 Senate
650. 2 Keys Keyboard
651. 4 Keys Keyboard

不会题：
659. Split Array into Consecutive Subsequences
667. Beautiful Arrangement II
672. Bulb Switcher II