26. Remove Duplicates from Sorted Array

Description

Given a sorted array nums, 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 by modifying the input array in-place with O(1) extra memory.

Example 1:

Given 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 returned length.

Example 2:

Given nums = [0,0,1,1,1,2,2,3,3,4],

Your function should return length = 5, with the first five elements of nums being modified to 0, 1, 2, 3, and 4 respectively.

It doesn't matter what values are set beyond the returned length.

Clarification:

Confused why the returned value is an integer but your answer is an array?

Note that the input array is passed in by reference, which means modification to the input array will be known to the caller as well.

Internally you can think of this:

// nums is passed in by reference. (i.e., without making a copy)
int len = removeDuplicates(nums);

// any modification to nums in your function would be known by the caller.
// using the length returned by your function, it prints the first len elements.
for (int i = 0; i < len; i++) {
    print(nums[i]);
}

Tags: Array, Two Pointers

题解

思路1

题意是让你从一个有序的数组中移除重复的元素,并返回之后数组的长度。我的思路是判断长度小于等于 1 的话直接返回原长度即可,否则的话遍历一遍数组,用一个 tail 变量指向尾部,如果后面的元素和前面的元素不同, 就让 tail 变量加一,最后返回 tail 即可。

func removeDuplicates(nums []int) int {
    if len(nums) <= 1 {
        return len(nums)
    }
    tail := 1
    for i := 1; i < len(nums); i++ {
        if nums[i-1] != nums[i] {
            nums[tail] = nums[i]
            tail++
        }
    }
    return tail
}

思路2

结语

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