LeetCode 26. Remove Duplicates from Sorted Array

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本文介绍了一种使用双指针技术在原地去除已排序数组中重复元素的方法，并返回新的长度。这种方法不需要额外分配数组空间，仅使用常数级别的内存就能完成任务。

Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length.

Do not allocate extra space for another array, you must do this in place with constant memory.

For example,
Given input array nums = [1,1,2],

Your function should return length = 2, with the first two elements of nums being 1 and 2 respectively. It doesn't matter what you leave beyond the new length.

// Two Pointers.

int removeDuplicates(vector<int>& nums) {
    if(nums.size() <= 1) return nums.size();
    int i = 0;  // first pointer
    int j = 1;  // second pointer
    while(j < nums.size()) {
        if(nums[i] != nums[j]) {
            nums[++i] = nums[j++];
        } else {
            j++;
        }
    }
    return i + 1;
}