3751. Total Waviness of Numbers in Range I

Description

You are given two integers num1 and num2 representing an inclusive range [num1, num2].

The waviness of a number is defined as the total count of its peaks and valleys:

• A digit is a peak if it is strictly greater than both of its immediate neighbors.
• A digit is a valley if it is strictly less than both of its immediate neighbors.
• The first and last digits of a number cannot be peaks or valleys.
• Any number with fewer than 3 digits has a waviness of 0.

Return the total sum of waviness for all numbers in the range [num1, num2].

 

Example 1:

Input: num1 = 120, num2 = 130

Output: 3

Explanation:

In the range [120, 130]:

• 120: middle digit 2 is a peak, waviness = 1.
• 121: middle digit 2 is a peak, waviness = 1.
• 130: middle digit 3 is a peak, waviness = 1.
• All other numbers in the range have a waviness of 0.

Thus, total waviness is 1 + 1 + 1 = 3.

Example 2:

Input: num1 = 198, num2 = 202

Output: 3

Explanation:

In the range [198, 202]:

• 198: middle digit 9 is a peak, waviness = 1.
• 201: middle digit 0 is a valley, waviness = 1.
• 202: middle digit 0 is a valley, waviness = 1.
• All other numbers in the range have a waviness of 0.

Thus, total waviness is 1 + 1 + 1 = 3.

Example 3:

Input: num1 = 4848, num2 = 4848

Output: 2

Explanation:

Number 4848: the second digit 8 is a peak, and the third digit 4 is a valley, giving a waviness of 2.

 

Constraints:

• 1 <= num1 <= num2 <= 105

 

Solutions

Solution: Simulation

• Time complexity: O(6n -> n)
  • n is num2 - num1 + 1
• Space complexity: O(1)

 

JavaScript

/**
 * @param {number} num1
 * @param {number} num2
 * @return {number}
 */
const totalWaviness = function (num1, num2) {
  const start = Math.max(num1, 100);
  const end = Math.max(num2, 100);
  let result = 0;

  const getWaviness = num => {
    const target = `${num}`;
    const n = target.length;
    let waviness = 0;

    for (let index = 1; index < n - 1; index++) {
      const current = target[index];
      const prev = target[index - 1];
      const next = target[index + 1];

      if (current < prev && current < next) {
        waviness += 1;
      }

      if (current > prev && current > next) {
        waviness += 1;
      }
    }

    return waviness;
  };

  for (let num = start; num <= end; num++) {
    result += getWaviness(num);
  }

  return result;
};