ALiTuTu的专栏

problem link: https://leetcode.com/problems/sort-characters-by-frequency/ note: 1.Java集合类priorityqueue优先队列，没用过所以想不到，还想自己写插入排序，Java现成的方法很方便 2.想到用桶排序的思想，但是由于考虑到string长度会不会太长以及中文字符的存在而放弃了 3.com

problem link code(java 2ms  beat 32.44%): public class Solution { public int numberOfArithmeticSlices(int[] A) { int count = 0; int N = A.length; if(N<=2){ return 0; } fo

注意边界及特殊情况 problem link:https://leetcode.com/problems/counting-bits/ code1(java 3ms): public class Solution { public int[] countBits(int num) { if(num==0){ return new

复杂度要求O(n)，不代表只能遍历一遍，可以遍历2遍、3遍。。。。 product--->名词：积 stem: Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of num