大锅八十小锅四十

Tag:Array,Hash Table **Difficulty: **Easy Description: Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j]

Tag Array,Hash Table Difficulty Easy Description Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least twice in the

454. 4Sum II：求满足A[i]+B[j]+C[k]+D[l] = 0的 (i,j,k,l)个数，Medium http://bookshadow.com/weblog/2016/11/13/leetcode-4sum-ii/ 利用字典cnt，将A，B中各元素（笛卡尔积）的和进行分类计数。 将C，D中各元素（笛卡尔积）和的相反数在cnt中的值进行累加，即为答案。...