按顺序做题，力求当前语言下的最优解。
目前进度为42条。

leetcode-cn	my code	remark
3sum	code
3sum closest	code
4sum	code
add two numbers	code
combination sum	code
combination sum ii	code
container with most water	code
count and say	code
divide two integers	code
find first and last position of element in sorted array	code
first missing positive	code
generate parentheses	code
implement strstr	code	应使用其他语言。
integer to roman	code
letter combinations of a phone number	code
longest common prefix	code
longest palindromic substring	code
longest substring without repeating characters	code
longest valid parentheses	code
median of two sorted arrays	code
merge k sorted lists	code
merge two sorted lists	code
next permutation	code
palindrome number	code
regular expression matching	code	应使用其他语言。
remove duplicates from sorted array	code
remove element	code
remove nth node from end of list	code
reverse integer	code
reverse nodes in k group	code
roman to integer	code
search in rotated sorted array	code
search insert position	code
string to integer atoi	code	应使用其他语言。
substring with concatenation of all words	code
sudoku solver	code	推理加试错，完成！
swap nodes in pairs	code
trapping rain water	code
two sum	code
valid parentheses	code
valid sudoku	code
zigzag conversion	code