摘要：
Given a string, sort it in decreasing order based on the frequency of characters. Example 1: Example 2: Example 3: 首先用hashmap扫一遍string，统计频率。按频率排序，将ha 阅读全文
摘要：
Given a non-empty array of integers, every element appears twice except for one. Find that single one. Note: Your algorithm should have a linear runti 阅读全文
摘要：
Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element. Example 阅读全文
摘要：
Design a class to find the kth largest element in a stream. Note that it is the kth largest element in the sorted order, not the kth distinct element. 阅读全文
摘要：
Given an array nums containing n + 1 integers where each integer is between 1 and n (inclusive), prove that at least one duplicate number must exist. 阅读全文