[ LeetCode ] [ JavaScript ] - 26. Remove Duplicates from Sorted Array 難度 ★ @ 西瓜是肥貓

官網題目敘述：

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.

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 modification to the input array will be known to the caller as well.

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]);
}

先附上通關證明（感覺應該有更好的方法，歡迎分享給我..)

截圖 2020-06-12 下午3.13.03

我的想法：

既然他陣列都已經排序過了，就很好做，遇到不同的數字在增加index就好，必且把新的數字放到index上面去就好，刷過一輪就排好了。

然後再照題目要求整理完後回傳這數列有多長。

然後把這個想法練習寫成 Js ：

/**
 * @param {number[]} nums
 * @return {number}
 */
var removeDuplicates = function(nums) {
    if(nums.length < 2) return nums.length;
    var index = 0
    var lastnum = false
    nums.forEach(num => {
        if(num!=lastnum) {
            nums[index] = num
            index++
            lastnum = num
        }
    });
    return index
};