[leetcode] Remove Duplicates from Sorted Array

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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].

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

思路：雙指標。指標i遍曆，指標j指向下一個unique的位置。注意corner case。

 

public class Solution {    public int removeDuplicates(int[] A) {        if (A == null)            return 0;        if (A.length < 1)            return A.length;        int n = A.length;        int len = 1;        for (int i = 1; i < n; i++) {            if (A[i] != A[i - 1])                A[len++] = A[i];        }        return len;    }    public static void main(String[] args) {        System.out.println(new Solution().removeDuplicates(new int[] { 1, 1, 1, 2 }));        System.out.println(new Solution().removeDuplicates(new int[] { 1, 1, 2, 2, 2, 2, 3, 3, 3, 4, 4, 5, 5 }));        System.out.println(new Solution().removeDuplicates(new int[] {}));        System.out.println(new Solution().removeDuplicates(new int[] { 1 }));        System.out.println(new Solution().removeDuplicates(new int[] { 1, 1 }));    }}