https://leetcode-cn.com/problems/remove-duplicates-from-sorted-array/submissions/

双指针

• done + cur 指针
• 左边是排好的区域（不断扩）， 中途是垃圾区域， 到最后垃圾区域都在右边

、

 public int removeDuplicates(int[] nums) {
      if (nums == null ) {
            return 0;
        }
        if (nums.length < 2) {
            return nums.length;
        }
        int done = 0;
        for (int i = 1; i < nums.length; i++) {
            if (nums[i] != nums[done]) {
                nums[++done] = nums[i];
            }
        }
        return done + 1;
 }