2269. Find the K-Beauty of a Number

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2269. Find the K-Beauty of a Number

Description

The k-beauty of an integer num is defined as the number of substrings of num when it is read as a string that meet the following conditions:

  • It has a length of k.
  • It is a divisor of num.

Given integers num and k, return the k-beauty of num.

Note:

  • Leading zeros are allowed.
  • 0 is not a divisor of any value.

A substring is a contiguous sequence of characters in a string.

Example 1:

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Input: num = 240, k = 2
Output: 2

Explanation: The following are the substrings of num of length k:

  • “24” from “24 0”: 24 is a divisor of 240.
  • “40” from “2 40 “: 40 is a divisor of 240.
    Therefore, the k-beauty is 2.

Example 2:

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Input: num = 430043, k = 2
Output: 2

Explanation: The following are the substrings of num of length k:

  • “43” from “ 43 0043”: 43 is a divisor of 430043.
  • “30” from “4 30 043”: 30 is not a divisor of 430043.
  • “00” from “43 00 43”: 0 is not a divisor of 430043.
  • “04” from “430 04 3”: 4 is not a divisor of 430043.
  • “43” from “4300 43 “: 43 is a divisor of 430043.
    Therefore, the k-beauty is 2.

Constraints:

  • 1 <= num <= 10^9
  • 1 <= k <= num.length (taking num as a string)

Hints/Notes

  • 2024/10/26
  • sliding window
  • No solution from 0x3F

Solution

Language: C++

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class Solution {
public:
    int divisorSubstrings(int num, int k) {
        string numStr = to_string(num), cur;
        int right = 0, n = numStr.size(), res = 0;
        while (right < n) {
            cur.push_back(numStr[right]);
            if (right >= k - 1) {
                int curNum = stoi(cur);
                if (curNum && num % stoi(cur) == 0) {
                    res++;
                }
                cur.erase(cur.begin());
            }
            right++;
        }
        return res;
    }
};