1. string to Integer (atoi) AC rate: 14.4%
https://oj.leetcode.com/problems/string-to-integer-atoi/

2. Longest Common Prefix AC rate: 27.1%
https://oj.leetcode.com/problems/longest-common-prefix/

3. minimum window substring  AC rate: 17.8%
https://oj.leetcode.com/problems/minimum-window-substring/

4. LRU cache AC rate: 13.3%
https://oj.leetcode.com/problems/lru-cache/

5. multiply strings AC rate: 20.3%
https://oj.leetcode.com/problems/multiply-strings/

6. Longest Substring Without Repeating Characters AC rate: 22.0%
https://oj.leetcode.com/problems/longest-substring-without-repeating-characters/