Viiisit [LeetCode] - 27. Remove Element

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Problem - Remove Element

Given an integer array nums and an integer val, remove all occurrences of val in nums in-place. The order of the elements may be changed. Then return the number of elements in nums which are not equal to val.

Consider the number of elements in nums which are not equal to val be k, to get accepted, you need to do the following things:

• Change the array nums such that the first k elements of nums contain the elements which are not equal to val. The remaining elements of nums are not important as well as the size of nums.
• Return k.

翻譯蒟蒻

題目要求要更改原始的 nums 陣列，最終的 k 值要返回陣列中不等於 val 元素的數量。

• Example 1:

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

• 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 k = 5, with the first five elements of nums containing 0, 0, 1, 3, and 4.
  Note that the five elements can be returned in any order.
  It does not matter what you leave beyond the returned k (hence they are underscores).

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Solution - JavaScript

Solution 1:

/**
 * @param {number[]} nums
 * @param {number} val
 * @return {number}
 */
var removeElement = function(nums, val) {
  for (let i = 0; i < nums.length; i++){
    if (nums[i] === val) {
      // 找到相同的元素之後要從原始陣列 nums 中移除
      nums.splice(i, 1);
      // 因為有從原始陣列 nums 中移除一個元素，需要將 i 減一，這樣下一次循環才會檢查當前索引的元素。
      i--;
    }
  }
};

Solution 2:

/**
 * @param {number[]} nums
 * @param {number} val
 * @return {number}
 */
var removeElement = function(nums, val) {
  let index = 0;
  for (let i = 0; i < nums.length; i++){
    if (nums[i] !== val) {
      nums[index++] = nums[i];
    }
  }
  return index;
};

Solution - Ruby

def remove_element(nums, val)
  # 刪除 num == val
  nums.delete(val)
  # 回傳 nums 的長度
  nums.length
end

nums = [1, 2, 3, 2, 4]
val = 2

result = remove_element(nums, val)
puts result

LeetCode 傳送門 - Remove Element