Leetcode

[LeetCode] 27. Remove Element

second9040

＊javascript solution
[easy] 27. Remove Element

Given an array nums and a value val, remove all instances of that value in-place 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.

The order of elements can be changed. It doesn't matter what you leave beyond the new 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 a 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 = removeElement(nums, val);

// 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 = [3,2,2,3], val = 3
Output: 2, nums = [2,2]
Explanation: Your function should return length = 2, with the first two elements of nums being 2.
It doesn't matter what you leave beyond the returned length. For example if you return 2 with nums = [2,2,3,3] or nums = [2,2,0,0], your answer will be accepted.

Example 2:

Input: nums = [0,1,2,2,3,0,4,2], val = 2
Output: 5, nums = [0,1,4,0,3]
Explanation: Your function should return length = 5, with the first five elements of nums containing 0, 1, 3, 0, and 4. Note that the order of those five elements can be arbitrary. It doesn't matter what values are set beyond the returned length.

Constraints:

0 <= nums.length <= 100

0 <= nums[i] <= 50

0 <= val <= 100

 

一開始的思路是... forEach 開下去?!!!
......

var removeElement = function(nums, val) {
    let newArr = []
    nums.forEach((x)=> {
        if(x!==val){
            newArr.push(x)
        }
    })
    return newArr
};

 

然後 output nothing ...
掙扎了五分鐘之後果斷放棄，雖然還是不知道為甚麼會 output nothing，但至少看了別人答案之後知道根本搞錯題目的意思...(這英文能力...TAT
 
重寫之後第一次還是被擋，結果原來是例外問題，加個例外判斷就過了

var removeElement = function(nums, val) {
    if (!nums || nums.length === 0) return 0;

    let index = 0
    for (let i in nums) {
      if (val !== nums[i]) {
        nums[index++] = nums[i]
      }
    }
    return index
};