swap the element if it's equal to "val"

```
class Solution(object):
def removeElement(self, nums, val):
"""
:type nums: List[int]
:type val: int
:rtype: int
"""
i, j = 0, 0
for j in range(len(nums)):
if nums[j] != val:
nums[i], nums[j] = nums[j], nums[i]
i += 1
return i
```