26. Remove Duplicates from Sorted Array

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.

class Solution {
public:
    int removeDuplicates(vector<int>& nums) {
        if(nums.size()<2) return nums.size();
        int id=1;
        for(int i=1;i<nums.size();i++)
        {
            if(nums[i]!=nums[i-1]) nums[id++]=nums[i];
        }
        return id;
    }
};

思想：这种做法的核心是记录出现某数i与该数前一个数i-1不一样时，把该数i所对应的数组中的数存入下标为id的位置，然后id加1，i也继续往后找。关键是不一样。