Remove Duplicates from Sorted Array

Description

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 by modifying the input array in-place with O(1) extra memory.

Example:

Given 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

题意是让你从一个有序的数组中移除重复的元素，并返回之后数组的长度。 此外，特别要注意，需要修改原数组。

判断长度小于等于 1 的话直接返回原长度即可，否则的话遍历一遍数组，用一个 tail 变量指向新的数组尾部，如果后面的元素和前面的元素不同，就让后面的元素写到 tail 所指数组元素，然后 tail 变量加一，最后返回 tail 即可。

实现代码

class Solution {
    public int removeDuplicates(int[] nums) {
        int len = nums.length;
        if (len <= 1) return len;

        int tail = 1;
        for (int i = 1; i < len; i++) {
            if (nums[i] != nums[i - 1]) {
                nums[tail++] = nums[i];
            }
        }

        return tail;
    }
}