LeetCode 2264. Largest 3-Same-Digit Number in String Solution in Java, C++, Python & More | Explanation + Code

Description

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.

Solutions

Solution 1: Enumeration

We can enumerate each digit i from large to small, where 0 \le i \le 9, and then check whether the string s consisting of three consecutive i is a substring of num. If it is, we directly return s.

If we have enumerated all the possible values of i and still haven't found a substring that satisfies the condition, we return an empty string.

The time complexity is O(10 × n), where n is the length of the string num. The space complexity is O(1).

PythonJavaC++GoTypeScript

class Solution: def largestGoodInteger(self, num: str) -> str: for i in range(9, -1, -1): if (s := str(i) * 3) in num: return s return ""(code-box)

class Solution { public String largestGoodInteger(String num) { for (int i = 9; i >= 0; i--) { String s = String.valueOf(i).repeat(3); if (num.contains(s)) { return s; } } return ""; } }(code-box)

class Solution { public: string largestGoodInteger(string num) { for (char i = '9'; i >= '0'; --i) { string s(3, i); if (num.find(s) != string::npos) { return s; } } return ""; } };(code-box)

func largestGoodInteger(num string) string { for c := '9'; c >= '0'; c-- { if s := strings.Repeat(string(c), 3); strings.Contains(num, s) { return s } } return "" }(code-box)

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