LeetCode - Remove Duplicates From Sorted Array(26)


26. Remove Duplicates From Sorted Array

Given an integer array nums sorted in non-decreasing order, remove the duplicates in-place such that each unique element appears only once. The relative order of the elements should be kept the same.

Since it is impossible to change the length of the array in some languages, you must instead have the result be placed in the first part of the array nums. More formally, if there are k elements after removing the duplicates, then the first k elements of nums should hold the final result. It does not matter what you leave beyond the first k elements.

Return k after placing the final result in the first k slots of nums.

Do not allocate extra space for another array. You must do this by modifying the input array in-place with O(1) extra memory.

Custom Judge:

The judge will test your solution with the following code:

int[] nums = [...]; // Input array
int[] expectedNums = [...]; // The expected answer with correct length

int k = removeDuplicates(nums); // Calls your implementation

assert k == expectedNums.length;
for (int i = 0; i < k; i++) {
    assert nums[i] == expectedNums[i];
}

If all assertions pass, then your solution will be accepted.

Example 1:

Input: nums = [1,1,2] Output: 2, nums = [1,2,_] Explanation: Your function should return k = 2, with the first two elements of nums being 1 and 2 respectively. It does not matter what you leave beyond the returned k (hence they are underscores). Example 2:

Input: nums = [0,0,1,1,1,2,2,3,3,4] Output: 5, nums = [0,1,2,3,4,,,,,_] Explanation: Your function should return k = 5, with the first five elements of nums being 0, 1, 2, 3, and 4 respectively. It does not matter what you leave beyond the returned k (hence they are underscores).

Constraints:

0 <= nums.length <= 3 * 104 -100 <= nums[i] <= 100 nums is sorted in non-decreasing order.

思考邏輯

這個問題某種程度上來說可以把它理解成重新排序。

我想要重排這個 array ,但不要有重複的數字,然後告訴我不重複的數字有幾個。

所以我會有一個指標從 0 開始,如果遇到不相同的數值,這個指標才會往前移動(發現不重複的數值),並將新值賦予進來。

直到 array 結束。

Solution

func removeDuplicates(nums []int) int {
    if len(nums) == 0 {
        return 0   
    }
    i := 0
    for j := 1; j < len(nums); j++ {
        if nums[i] != nums[j] {
            i ++
            nums[i] = nums[j]
        }
    }
    return i + 1
}
Array 

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