4057 Total Waviness Of Numbers In Range I

Total Waviness of Numbers in Range I

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

class Solution:
    def totalWaviness(self, num1: int, num2: int) -> int:
        def waviness(n: int) -> int:
            s = str(n)
            return sum(
                (a < b > c) or (a > b < c) for a, b, c in zip(s, s[1:], s[2:])
            )

        return sum(waviness(n) for n in range(num1, num2 + 1))