[LeetCode]026. Remove Duplicates from Sorted Array

最新推荐文章于 2025-08-10 20:50:18 发布

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本文介绍了一种使用双指针技术在原地去除已排序数组中重复元素的方法，并返回新的长度。该方法不需要额外的空间，仅使用常数级别的内存。

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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 A = [1,1,2],

Your function should return length = 2, and A is now [1,2].

Solutions:

use two pointers(indices),

at first, head=0, next=0,

if there is a duplicate digit, next++;

or copy the A[next] to A[head+1], head++, next++.

public class Solution {
    public int removeDuplicates(int[] A) {
        // Start typing your Java solution below
        // DO NOT write main() function
        int n = A.length;
        if(n==0){
            return 0;
        }
        if(n==1){
            return 1;
        }
        // must consider above two cases;
        
        int head = 0;
        int next = 0;
        int newLength = 0;
        while(next<n){
            if(A[head] == A[next]){
                next++;
            }else{
                A[head+1] = A[next];
                head++;
                next++;
            }
        }
        return newLength = head+1;
    }
}