Some of the annotated solutions above were also posted on the leetcode forum:
3. Longest Substring Without Repeating Characters — C++ solution
309. Best Time to Buy and Sell Stock with Cooldown — Python solution
342. Power of Four — Python solution
368. Largest Divisible Subset — Java solution
388. Longest Absolute File Path — C++ solution
401. Binary Watch — C++ solution
402. Remove K Digits — C++ solution
421. Maximum XOR of Two Numbers in an Array — C++ solution