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