136. Single Number
Given an array of integers, every element appears twice except for one. Find that single one.
Bit: a ^ a = 0;
public class Solution { public int singleNumber(int[] nums) { int res = 0; for(int n : nums){ res ^= n; } return res; } }
137. Single Number II
public class Solution { public int singleNumber(int[] nums) { HashMap<Integer, Integer> map = new HashMap<>(); for(int i = 0 ; i < nums.length ; i++){ map.put(nums[i], map.getOrDefault(nums[i], 0) + 1); } for(Map.Entry<Integer, Integer> entry : map.entrySet()){ if(entry.getValue() == 1) return entry.getKey(); } return 0; } }
260. Single Number III
Given an array of numbers nums
, in which exactly two elements appear only once and all the other elements appear exactly twice. Find the two elements that appear only once.
For example:
Given nums = [1, 2, 1, 3, 2, 5]
, return [3, 5]
.
public class Solution { public int[] singleNumber(int[] nums) { Set<Integer> set = new HashSet<>(); for(int n: nums){ if(!set.add(n)){ set.remove(n); } } Iterator<Integer> it = set.iterator(); int[] res = new int[2]; int start = 0; while(it.hasNext() && start < res.length){ res[start] = it.next(); start++; } return res; } }
二刷可以研究bit做法
时间: 2024-10-06 08:06:50