27. Remove Element

Given input array nums = [3,2,2,3], val = 3

Your function should return length = 2, with the first two elements of nums being 2.
就是把不是3的元素往前移动至队首，再返回不是３的元素个数．
\(O(n)\) time, \(O(0)\) space.

int removeElement(vector<int> nums, int val){
	int i = 0, k = 0;
	while(i < nums.size()){
		if(nums[i] != val)
			nums[k++] = nums[i];
		i++;
	}
	return k;
}