You are given a string num
representing a large integer. An integer is good if it meets the following conditions:
- It is a substring of
num
with length3
. - It consists of only one unique digit.
Return the maximum good integer as a string or an empty string ""
if no such integer exists.
Note:
- A substring is a contiguous sequence of characters within a string.
- There may be leading zeroes in
num
or a good integer.
Example 1:
Input: num = "6777133339" Output: "777" Explanation: There are two distinct good integers: "777" and "333". "777" is the largest, so we return "777".
Example 2:
Input: num = "2300019" Output: "000" Explanation: "000" is the only good integer.
Example 3:
Input: num = "42352338" Output: "" Explanation: No substring of length 3 consists of only one unique digit. Therefore, there are no good integers.
Constraints:
3 <= num.length <= 1000
num
only consists of digits.
Solution:
Time complexity: O(n)
Space complexity: O(1)
C++
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// Author: Huahua class Solution { public: string largestGoodInteger(string num) { string ans; for (int i = 0; i < num.size() - 2; ++i) { if (num[i] == num[i + 1] && num[i] == num[i + 2] && (ans.empty() || num[i] > ans[0])) ans = num.substr(i, 3); } return ans; } }; |
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