leetcode刷题系列C++-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.

Subscribe to see which companies asked this question

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

第一个元素肯定不会重复，从第二个开始起，跟前一个进行比较，如果相同，则循环继续，index不增，如果出现了不同，将元素记录在当前的index索引处，index增加一，继续比较。时间复杂度为一次遍历O(n)，空间复杂度为O(1),为in place 操作

对于数组来说，在内存中是分配在栈上的，不需要程序员去管理内存，不用担心vector类型的nums ，去重后大小比原来小了，重复的元素所占的空间如何去掉的问题。