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:
Input: num = 240, k = 2 Output: 2 Explanation: The following are the substrings of num of length k: - "24" from "240": 24 is a divisor of 240. - "40" from "240": 40 is a divisor of 240. Therefore, the k-beauty is 2.
Example 2:
Input: num = 430043, k = 2 Output: 2 Explanation: The following are the substrings of num of length k: - "43" from "430043": 43 is a divisor of 430043. - "30" from "430043": 30 is not a divisor of 430043. - "00" from "430043": 0 is not a divisor of 430043. - "04" from "430043": 4 is not a divisor of 430043. - "43" from "430043": 43 is a divisor of 430043. Therefore, the k-beauty is 2.
Constraints:
1 <= num <= 109
1 <= k <= num.length
(takingnum
as a string)
Solution: Substring
Note: the substring can be 0, e.g. “00”
Time complexity: O((l-k)*k)
Space complexity: O(l + k) -> O(1)
C++
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// Author: Huahua class Solution { public: int divisorSubstrings(int num, int k) { string s = to_string(num); int ans = 0; for (int i = 0; i <= s.length() - k; ++i) { const int t = stoi(s.substr(i, k)); ans += t && (num % t == 0); } return ans; } }; |
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