Leetcode 26 Remove duplicate elements

题意：在有序数组中删除重复元素

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

解法：双指针,i记录答案，j遇到重复的值就往后跳过

class Solution {
public:
    int removeDuplicates(vector<int>& nums) {
        int i = 0;
        for(int j = 0; j < nums.size(); j++) {
            while (j > 0 && j < nums.size() && nums[j] == nums[j-1]) {
                j++;
            } 
            if(j < nums.size()) {
                nums[i++] = nums[j];
            }
        }
        return i;
    }
};

解法二：双指针，但是判断的条件是略有不同，是判断j指向元素和i指向元素是否重复，代码更为简洁

class Solution {
 public:
  int removeDuplicates(vector<int>& a) {
    int i = 0;
    for (int j = 0; j < a.size(); j++)
      if (!i || a[j] != a[i - 1]) a[i++] = a[j];

    return i;
  }
};

时间复杂度$O(n)$
空间复杂度$O(1)$