3903. Smallest Stable Index I

Easy

題目描述

Description

You are given an integer array nums of length n and an integer k.

For each index i, define its instability score as max(nums[0..i]) - min(nums[i..n - 1]).

In other words:

• max(nums[0..i]) is the largest value among the elements from index 0 to index i.
• min(nums[i..n - 1]) is the smallest value among the elements from index i to index n - 1.

An index i is called stable if its instability score is less than or equal to k.

Return the smallest stable index. If no such index exists, return -1.

Example 1:

Input: nums = [5,0,1,4], k = 3

Output: 3

Explanation:

• At index 0: The maximum in [5] is 5, and the minimum in [5, 0, 1, 4] is 0, so the instability score is 5 - 0 = 5.
• At index 1: The maximum in [5, 0] is 5, and the minimum in [0, 1, 4] is 0, so the instability score is 5 - 0 = 5.
• At index 2: The maximum in [5, 0, 1] is 5, and the minimum in [1, 4] is 1, so the instability score is 5 - 1 = 4.
• At index 3: The maximum in [5, 0, 1, 4] is 5, and the minimum in [4] is 4, so the instability score is 5 - 4 = 1.
• This is the first index with an instability score less than or equal to k = 3. Thus, the answer is 3.

Example 2:

Input: nums = [3,2,1], k = 1

Output: -1

Explanation:

• At index 0, the instability score is 3 - 1 = 2.
• At index 1, the instability score is 3 - 1 = 2.
• At index 2, the instability score is 3 - 1 = 2.
• None of these values is less than or equal to k = 1, so the answer is -1.

Example 3:

Input: nums = [0], k = 0

Output: 0

Explanation:

At index 0, the instability score is 0 - 0 = 0, which is less than or equal to k = 0. Therefore, the answer is 0.

Constraints:

• 1 <= nums.length <= 100
• 0 <= nums[i] <= 10^9
• 0 <= k <= 10^9

解答

Solution

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {number}
 */
var firstStableIndex = function (nums, k) {
  for (let i = 0; i < nums.length; i++) {
    const maximum = Math.max(...nums.slice(0, i + 1));
    const minimum = Math.min(...nums.slice(i));

    if (maximum - minimum <= k) return i;
  }

  return -1;
};

解題思路

提示寫 Simulate as described，所以就直接按照描述暴力解。

心得

目前時間複雜度是 O(n²)，滿差的，有很大的調整空間。