此題要求將輸入的已排序陣列移除重複的項目，必須在同一陣列下操作，最後回傳陣列之長度。
Given a sorted array nums, 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 1:
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 returned length.
Example 2:
Given nums = [0,0,1,1,1,2,2,3,3,4], Your function should return length = 5, with the first five elements of nums being modified to 0, 1, 2, 3, and 4 respectively. It doesn't matter what values are set beyond the returned length.
解題思路:
首先設定一個i用來記錄目前存放到哪個位置，再設定一個j用以完整遍歷整個陣列，
每當發現有不同的數字時，就將j的數字塞到i的位置，再往下推進即可。
using System;
namespace Remove_Duplicates_from_Sorted_Array
{
class Program
{
static void Main(string[] args)
{
int[] arr = new int[] {0, 0, 1, 1, 1, 2, 2, 3, 3, 4};
var result = removeDuplicates(arr);
}
public static int removeDuplicates(int[] nums)
{
if (nums.Length <= 1) return nums.Length;
int i = 0;
for (int j = 1; j < nums.Length; j++)
{
if (nums[j] != nums[i])
{
i++;
nums[i] = nums[j];
}
}
return i + 1;
}
}
}
Complexity analysis
-
Time complextiy : O(n). Assume that n is the length of array. Each of i and j traverses at most n steps.
-
Space complexity : O(1)
