Single number Leetcode Java

Problem Description:

Given an array of integers, every element appears twice except for one. Find the single one.

Note:
Your algorithm should has a linear runtime complexity. Could you implement it without using extra memory?

problem Analysis: linear time complexity is required, and it is best not to use extra space.

One, bit operation

An XOR operation that returns 1 only if the two bits are different. If the two numbers are the same, the XOR operation will return 0.

The nums contains only a single number, so, using an XOR operation, the last thing you get is the number you are seeking.

public int singlenumber (int[] nums) {

int single = 0;

for (int i = 0; i < nums.length; i + +)

Single = single ^ nums[i];

return single;

}

Second, HashSet

Compared to Hashtable,hashmap stored key-value key-value pairs, hashset directly manipulate objects and do not allow duplicate elements to be stored.

public int singlenumber (int[] nums) {

hashset<integer> set = new hashset<integer> ();

for (int i = 0; i < nums.length; i + +)

if (!set.add (Nums[i]))//Add Duplicate

Set.remove (Nums[i]); Delete duplicate elements

iterator<integer> Iterator = Set.iterator (); Iterator, traversing set

return Iterator.next ();

}

Single number Leetcode Java