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Formatted question description: https://leetcode.ca/all/2264.html

2264. Largest 3-Same-Digit Number in String

• Difficulty: Easy.
• Related Topics: String.
• Similar Questions: Largest Odd Number in String.

Problem

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 (Java, C++, Python)

• Java
• Python
• C++
• Go
• TypeScript

• class Solution {
      public String largestGoodInteger(String num) {
          String maxi = "000";
          int c = 0;
          for (int i = 0; i < num.length() - 2; i++) {
              String s = num.substring(i, i + 3);
              if (s.charAt(0) == s.charAt(1) && s.charAt(1) == s.charAt(2)) {
                  if (s.compareTo(maxi) >= 0) {
                      maxi = s;
                  }
                  ++c;
              }
          }
          if (c == 0) {
              return "";
          }
          return maxi;
      }
  }
  
  ############
  
  class Solution {
      public String largestGoodInteger(String num) {
          for (int i = 9; i >= 0; i--) {
              String ret = String.valueOf(i).repeat(3);
              if (num.contains(ret)) {
                  return ret;
              }
          }
          return "";
      }
  }
  
  

• class Solution:
      def largestGoodInteger(self, num: str) -> str:
          for i in range(9, -1, -1):
              t = str(i) * 3
              if t in num:
                  return t
          return ''
  
  ############
  
  # 2264. Largest 3-Same-Digit Number in String
  # https://leetcode.com/problems/largest-3-same-digit-number-in-string/
  
  class Solution:
      def largestGoodInteger(self, num: str) -> str:
          res = ""
  
          for key, group in itertools.groupby(num):
              if len(list(group)) >= 3:
                  res = max(res, key * 3)
  
          return res
                  
  
  

• class Solution {
  public:
      string largestGoodInteger(string num) {
          for (char i = '9'; i >= '0'; --i) {
              string t(3, i);
              if (num.find(t) != string::npos) return t;
          }
          return "";
      }
  };
  

• func largestGoodInteger(num string) string {
  	for c := '9'; c >= '0'; c-- {
  		t := strings.Repeat(string(c), 3)
  		if strings.Contains(num, t) {
  			return t
  		}
  	}
  	return ""
  }
  

• function largestGoodInteger(num: string): string {
      for (let i = 9; i >= 0; i--) {
          const c = String(i).repeat(3);
          if (num.includes(c)) return c;
      }
      return '';
  }
  
  

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).

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