【LeetCode】26. Remove Duplicates from Sorted Array

Difficulty:easy

 More:【目錄】LeetCode Java實現

Description

https://leetcode.com/problems/remove-duplicates-from-sorted-array/

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 = , with the first two elements of  being  and  respectively.

It doesn't matter what you leave beyond the returned length.2nums12

Example 2:

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

Your function should return length = , with the first five elements of  being modified to , , , , and  respectively.

It doesn't matter what values are set beyond the returned length.
5nums01234

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]);
}

Intuition

1. Two pointer.

 

Solution

class Solution {
    public int removeDuplicates(int[] nums) {
        if(nums==null || nums.length<=0)
            return 0;
        int i=0,j=1;
        while(j<nums.length){
            if(nums[i]==nums[j])
                j++;
            else
                nums[++i]=nums[j++];
        }
        return i+1;
    }
}

　　

Complexity

Time complexity : O(n)

Space complexity : O(1)

 

 More:【目錄】LeetCode Java實現