Remove Duplicates from Sorted Array

Given a sorted array, remove the duplicatesin-placesuch that each element appear onlyonceand return the new length.

Do not allocate extra space for another array, you must do this bymodifying the input arrayin-placewith 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.

图解

分析

1. two pointers : slow and fast, initially to be 1
2. scan the array from index 1 to rightmost using fast pointer, when nums[fast] is not equal to nums[fast-1], we assign nums[fast] to nums[slow] and increment slow

代码

class Solution {
    public int removeDuplicates(int[] nums) {
        if(nums.length == 0) return 0;

        int slow = 1;
        for(int i = 1; i< nums.length ; i++){
            if(nums[i]!=nums[i-1]){
                nums[slow]=nums[i];
                slow ++;
            }
        }
        return slow;
    }
}