LeetCode 26. Remove Duplicates from Sorted Array 删除排序数组中的重复数字

题目

https://leetcode.com/problems/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.

讲解

输入数列是已排好序的,所以我们可以用两个指针来解决这个问题。

nums[i] = nums[j]时,我们移动快指针。

nums[j] != nums[i]时,我们移动慢指针i,并用当前快指针位置的元素值来更新慢指针位置的元素值。

最后当快指针j到达数列最末,不重复的元素都已调整在数列前面位置了。

视频教学

Java参考代码

class Solution {
    public int removeDuplicates(int[] nums) {
        if (nums == null || nums.length == 0) {
            return 0;
        }
        
        int i = 0;
        
        for (int j = 0; j < nums.length; j++) {
            if (nums[j] != nums[i]) {
                i++;
                nums[i] = nums[j];
            }            
        }
        
        return i + 1;
        // Time Complextiy: O(n)
        // Space Complexity: O(1)
    }
}

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