Today I have done leetcode's December LeetCoding Challenge with cpp.

December LeetCoding Challenge 4

Description

Largest 3-Same-Digit Number in String

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 length 3.
• 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

class Solution {
public:
  string largestGoodInteger(string num) {
    string answer = "";
    char current = 0;
    for(int i = 2; i < num.size(); ++i) {
      if(num[i] == num[i - 1] && num[i] == num[i - 2] && num[i] > current) {
        answer = num.substr(i - 2, 3);
        current = num[i];
      }
    }

    return answer;
  }
};

// Accepted
// 141/141 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 59.71 % of cpp submissions (6.8 MB)