26. Remove Duplicates from Sorted Array

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 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 new length.

思路: 做到spaceO(1),需要两个指针,一个用来遍历数组,一个用来指向不重复的数据。

public class Solution {
    public int removeDuplicates(int[] nums) {
        if (nums == null || nums.length == 0) return 0;
        if (nums.length == 1) return 1;
        int newIdx = 0;
        for (int i = 1; i < nums.length; i++) {
            if (nums[i] != nums[newIdx]) {
                newIdx++;
                nums[newIdx] = nums[i];
            }
        }
        return newIdx+1;

    }
}

变体1. 如果允许重复数字最多可以出现k次, 则返回的长度为。

思路: 需要用一个count来记录重复次数最多出现的k次, 来确保最多出现k次

public class Solution {
    public int removeDuplicates(int[] nums, int k) {
        if (nums == null || nums.length == 0) return 0;
        if (nums.length == 1) return 1;
        int newIdx = 0;
        int count = 1;
        for (int i = 1; i < nums.length; i++) {
            if (nums[i] != nums[newIdx]) {
                newIdx++;
                count = 1;
                nums[newIdx] = nums[i];
            } else {
                if(count > k) continue; // 超过k次则 continue
                else {
                     nums[newIdx] = nums[i];
                     newIdx++;
                }

         }
        }
        return newIdx+1;

    }
}
Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s