LeetCode 2264: Largest 3-Same-Digit Number in String

Meta Data

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Difficulty: easy First Attempt: 2025-08-14

• Submissions: Accepted (first try)

Approach

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A good integer must look like "ddd", so there are only 10. From the largest, "999", down, the first one found in num is the answer (String Template 3).

My Solution

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I originally used a length-3 sliding window with a Counter, comparing with the current answer whenever the window held one character. Enumerating the 10 candidates is simpler:

class Solution:
    def largestGoodInteger(self, num: str) -> str:
        for d in "9876543210":
            if d * 3 in num:
                return d * 3
        return ""

Complexity

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Time O(10 · n), space O(1).

Mistakes to Avoid

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• The answer is a string, and "000" is valid; do not convert to an integer.

Interview Explanation

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Good integers are only "000" through "999", so I check from largest to smallest which appears in the string; the first found is the answer. Time O(n).