[Leetcode] Remove Duplicates from Sorted Array

描述

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.

分析

去除有序数组中重复元素并返回去重后的数组长度。

因为数组是有序的，因此如果有重复值，每个重复值都是连续的一片区域，因此我们可以使用双指针，一个指针用来遍历数组同时找出不重复的元素，另一个指针用来存储不重复的元素，时间复杂度 O(n)。

代码

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