[LeetCode] Remove Duplicates from Sorted Array

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

双指针，一个指针记录当前不重复的数字，另一个往前找

代码

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

Remove Duplicates from Sorted Array II

思路

代码

public int removeDuplicates(int[] nums) {
    //corner case
    if(nums == null || nums.length == 0) return 0;
    if(nums.length <= 2) return 2;
    int slow = 0, count = 1;
    for(int fast = 1; fast < nums.length; fast++){
        if(nums[slow] == nums[fast] && count < 2){
            slow++;
            nums[slow] = nums[fast];
            count++;
        }else if(nums[slow] != nums[fast]){
            slow++;
            nums[slow] = nums[fast];
            count = 1;
        }
    }
    return slow + 1;
}