题目
80 删除有序数组中的重复项 2
80 Remove Duplicates from Sorted Array II
描述
中文
给你一个有序数组 nums ，请你 原地 删除重复出现的元素，使每个元素 最多出现两次 ，返回删除后数组的新长度。
不要使用额外的数组空间，你必须在 原地 修改输入数组 并在使用 O(1) 额外空间的条件下完成。
说明：
为什么返回数值是整数，但输出的答案是数组呢？
请注意，输入数组是以「引用」方式传递的，这意味着在函数里修改输入数组对于调用者是可见的。
你可以想象内部操作如下:
// nums 是以“引用”方式传递的。也就是说，不对实参做任何拷贝 int len = removeDuplicates(nums); // 在函数里修改输入数组对于调用者是可见的。 // 根据你的函数返回的长度, 它会打印出数组中 该长度范围内 的所有元素。 for (int i = 0; i < len; i++) { print(nums[i]); }示例 1：
输入：nums = [1,1,1,2,2,3] 输出：5, nums = [1,1,2,2,3] 解释：函数应返回新长度 length = 5, 并且原数组的前五个元素被修改为 1, 1, 2, 2, 3 。 不需要考虑数组中超出新长度后面的元素。示例 2：
输入：nums = [0,0,1,1,1,1,2,3,3] 输出：7, nums = [0,0,1,1,2,3,3] 解释：函数应返回新长度 length = 7, 并且原数组的前五个元素被修改为 0, 0, 1, 1, 2, 3, 3 。 不需要考虑数组中超出新长度后面的元素。提示：
1 <= nums.length <= 3 * 104 -104 <= nums[i] <= 104 nums 已按升序排列
英文
Given a sorted array nums, remove the duplicates in-place such that duplicates appeared at most twice 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.
Clarification:
Confused why the returned value is an integer, but your answer is an array?
Note that the input array is passed in by reference, which means a modification to the input array will be known to the caller.
Internally you can think of this:
// nums is passed in by reference. (i.e., without making a copy) int len = removeDuplicates(nums); // any modification to nums in your function would be known by the caller. // using the length returned by your function, it prints the first len elements. for (int i = 0; i < len; i++) { print(nums[i]); }Example 1:
Input: nums = [1,1,1,2,2,3] Output: 5, nums = [1,1,2,2,3] Explanation: Your function should return length = 5, with the first five elements of nums being 1, 1, 2, 2 and 3 respectively. It doesn't matter what you leave beyond the returned length.Example 2:
Input: nums = [0,0,1,1,1,1,2,3,3] Output: 7, nums = [0,0,1,1,2,3,3] Explanation: Your function should return length = 7, with the first seven elements of nums being modified to 0, 0, 1, 1, 2, 3 and 3 respectively. It doesn't matter what values are set beyond the returned length.Constraints:
1 <= nums.length <= 3 * 104 -104 <= nums[i] <= 104 nums is sorted in ascending order.
分析
题目重点 : 有序数组 , 重复元素都是挨在一起的
可以使用快慢指针 , 当快慢两个指针值相同且距离=2时 , 即为题中的重复元素超过两个
数组中删除元素速度较慢 , 所以我们采用把正确的值直接填充到正确的位置
超过两个重复元素的部分不填充即可
代码
java
class Solution {
public int removeDuplicates(int[] nums) {
int i = 0;
for (int n : nums)
if (i < 2 || n > nums[i-2])
nums[i++] = n;
return i;
}
}