摘要：
Design a data structure that supports all following operations in average O(1) time. Note: Duplicate elements are allowed. Example: 阅读全文
摘要：
Given an Android 3x3 key lock screen and two integers m and n, where 1 ≤ m ≤ n ≤ 9, count the total number of unlock patterns of the Android lock scre 阅读全文
摘要：
Given a n x n matrix where each of the rows and columns are sorted in ascending order, find the kth smallest element in the matrix. Note that it is th 阅读全文