[leetcode] Remove Duplicates from Sorted Array II

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Follow up for "Remove Duplicates":
What if duplicates are allowed at most twice?

For example,
Given sorted array A = [1,1,1,2,2,3],

Your function should return length = 5, and A is now [1,1,2,2,3].

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

 

思路：雙指標法。只不過這次是前面隔一個元素比較。

 

public class Solution {    public int removeDuplicates(int[] A) {        int n = A.length;        if (n <= 2)            return n;        int index = 2;        for (int i = 2; i < n; i++) {            if (A[i] != A[index - 2])                A[index++] = A[i];        }        return index;    }    public int removeDuplicates2(int[] A) {        if (A.length <= 2)            return A.length;        int prev = 1; // point to previous        int curr = 2; // point to current        while (curr < A.length) {            if (A[curr] == A[prev] && A[curr] == A[prev - 1]) {                curr++;            } else {                prev++;                A[prev] = A[curr];                curr++;            }        }        return prev + 1;    }    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 }));    }}

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參考：

http://www.programcreek.com/2013/01/leetcode-remove-duplicates-from-sorted-array-ii-java/

http://zhangxc.com/2013/11/leetcode-remove-duplicates-from-sorted-array-2