LeetCode从排序数组或者链表中删除重复数字的问题

关于我的 Leetcode 题目解答，代码前往 Github：https://github.com/chenxiangcyr/leetcode-answers

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LeetCode题目：26. Remove Duplicates from Sorted Array
Given a sorted array nums, remove the duplicates in-place such that each element appear only once and return the new length.

class Solution {
    public int removeDuplicates(int[] nums) {
        int i = 0;
        
        for(int n : nums) {
            if(i < 1 || n > nums[i - 1]) {
                nums[i] = n;
                i++;
            }
        }
        
        return i;
    }
}

LeetCode题目：80. Remove Duplicates from Sorted Array II
Follow up for "Remove Duplicates":
What if duplicates are allowed at most twice?
For example,
Given sorted array nums = [1,1,1,2,2,3],
Your function should return length = 5, with the first five elements of nums being 1, 1, 2, 2 and 3. It doesn't matter what you leave beyond the new length.

class Solution {
    public int removeDuplicates(int[] nums) {
        int i = 0;
        
        for(int n : nums) {
            if(i < 2 || n > nums[i - 2]) {
                nums[i] = n;
                i++;
            }
        }
        
        return i;
    }
}

LeetCode题目：83. Remove Duplicates from Sorted List
Given a sorted linked list, delete all duplicates such that each element appear only once.
For example,
Given 1->1->2, return 1->2.
Given 1->1->2->3->3, return 1->2->3.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        ListNode cur = head;
        
        while(cur != null && cur.next != null) {
            if(cur.val == cur.next.val) {
                cur.next = cur.next.next;
            }
            else {
                cur = cur.next;
            }
        }
        
        
        return head;
    }
}

LeetCode题目：82. Remove Duplicates from Sorted List II
Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.
For example,
Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        ListNode dummyHead = new ListNode(-1);
        dummyHead.next = head;
        
        ListNode pre = dummyHead;
        ListNode cur = head;
        
        while(cur != null) {
            while(cur.next != null && cur.val == cur.next.val) {
                cur = cur.next;
            }
            
            if(pre.next == cur) {
                pre = pre.next;
            }
            else {
                pre.next = cur.next;
            }
            
            cur = cur.next;
        }
        
        return dummyHead.next;
    }
}