Given a set of distinct integers, S, return all possible subsets. Note: Elements in a subset must be in non-descending order. The solution set must not contain duplicate subsets. For example,If S =[1,2,3], a solution is: [ [3], [1], [2], [1,2,3], [1,…

[题目] Given a collection of integers that might contain duplicates, nums, return all possible subsets (the power set). Note: The solution set must not contain duplicate subsets. [思路] 注意sort,使得判断临接元素是否相邻. 与leetcode78类似,多了一个重复数判断条件 if(i>flag&&nums…

Given a collection of integers that might contain duplicates, S, return all possible subsets. Note: Elements in a subset must be in non-descending order. The solution set must not contain duplicate subsets. For example,If S =[1,2,2], a solution is: […

[题目] Given a set of distinct integers, nums, return all possible subsets (the power set). Note: The solution set must not contain duplicate subsets. 求子集,无重复数 [思路] 1.有回溯法模板 2.将tmp加入进ans.tmp用来存放第i个元素的子集.回溯产生第i个元素与其后[i+1,len]元素产生的子集(i-1前已经产生过,不重复遍历).因第i…

[题目] Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers. Note: All numbers will be positive integers. The solution set must not…

Leetcode之回溯法专题-90. 子集 II(Subsets II) 给定一个可能包含重复元素的整数数组 nums,返回该数组所有可能的子集(幂集). 说明:解集不能包含重复的子集. 示例: 输入: [1,2,2] 输出: [ [2], [1], [1,2,2], [2,2], [1,2], [] ] 分析:是78题的升级版,新增了一些限制条件,nums数组是会重复的,求子集. class Solution { List<List<Integer>> ans = new Arr…

Leetcode之回溯法专题-78. 子集(Subsets) 给定一组不含重复元素的整数数组 nums,返回该数组所有可能的子集(幂集). 说明:解集不能包含重复的子集. 示例: 输入: nums = [1,2,3] 输出: [ [3],   [1],   [2],   [1,2,3],   [1,3],   [2,3],   [1,2],   [] ] 分析:这题也是很基础的关于回溯法的一题,题中给一个数组,求他的子集(包括空集). AC代码: class Solution { List<Li…

A peak element is an element that is greater than its neighbors. Given an input array where num[i] ≠ num[i+1], find a peak element and return its index. The array may contain multiple peaks, in that case return the index to any one of the peaks is fi…

题目意思:求解一个数组的所有子集,子集内的元素增序排列eg:[1,3,2] result:[],[1],[2],[1,2],[3],[1,3],[2,3],[1,2,3]思路:这是一个递推的过程 [] []+[1] [2]+[1,2]+[]+[1] 第k项的子集为第k个数分别加到k-1项的子集,再加上k-1项的子集程序过程:------------------- ans[0] []------------------- ans[1] [1]------------------- ans[2] […

求集合的所有子集问题 LeetCode:Subsets Given a set of distinct integers, S, return all possible subsets. Note: Elements in a subset must be in non-descending order. The solution set must not contain duplicate subsets. For example,If S = [1,2,3], a solution is:…