# Leetcode No.136
**[題目連結](https://leetcode.com/problems/single-number/description/)**
## Python
```python=
class Solution:
def singleNumber(self, nums: List[int]) -> int:
collect_list = []
for num in nums:
if num in collect_list:
collect_list.remove(num)
else:
collect_list.append(num)
return collect_list[0]
```
### 其他解法
1. 將nums取set後的所有數字總和乘以2，減去nums的數字總和
```python
class Solution:
def singleNumber(self, nums: List[int]) -> int:
return 2*sum(set(nums))-sum(nums)
```