1
// two pointer
2
class Solution {
3
 public:
4
  int removeElement(vector<int> &nums, int val) {
5
    int left = 0;
6
    int right = nums.size() - 1;
7
    while (left <= right) {
8
      if (nums[left] != val) {
9
        ++left;
10
      } else if (nums[right] == val) {
11
        --right;
12
      } else if (left < right) {
13
        nums[left++] = nums[right--];
14
      }
15
    }
16
    return left;
17
  }
18
};