摘要： Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: No 阅读全文

摘要： Given an array of integers where 1 ≤ a[i] ≤ n (n= size of array), some elements appear twice and others appear once. Find all the elements of [1, n] i 阅读全文