[LeetCode]136. Single Number

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

解法一：连连看方法

public int singleNumber2(int[] nums) {
<span style="white-space:pre">	</span>HashSet<Integer> h=new HashSet<Integer>();
<span style="white-space:pre">	</span>for(int i=0; i<nums.length ; i++)
<span style="white-space:pre">		</span>if(h.contains(nums[i]))
<span style="white-space:pre">		</span>h.remove(nums[i]);
<span style="white-space:pre">		</span>else
<span style="white-space:pre">		</span>h.add(nums[i]);
<span style="white-space:pre">	</span>Iterator<Integer> iterator = h.iterator();
<span style="white-space:pre">	</span>eturn (int) iterator.next();
}

解法二：位运算法

public int singleNumber3(int[] nums) {
int res = 0;
for (int i = 0; i < nums.length; i++)
res = res^nums[i];
return res;
}