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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)

• 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).