3536: Maximum Product of Two Digits

Problem Statement

Given a positive integer n, return the maximum product of any two digits in n. You may use the same digit twice if it appears more than once.

Example 1

Input: n = 31
Output: 3
Explanation: Possible product is 3 × 1 = 3

Example 2

Input: n = 22
Output: 4
Explanation: Possible product is 2 × 2 = 4

Example 3

Input: n = 124
Output: 8
Explanation: Possible product is 2 × 4 = 8

Approach 1: Digit Extraction & Sorting (Optimal)

Extract digits, sort them, and calculate product of largest two digits.

Algorithm Steps

1. Convert number to string to extract digits
2. Convert characters to integers
3. Sort digits in descending order
4. Return product of first two digits

Complexity Analysis

class maxProduct {
public:
    int maxProduct(int n) {
        string s = to_string(n);
        if(s.size() < 2) return 0;
        vector<int> digits;
        for(char c : s) {
            digits.push_back(c - '0');
        }
        sort(digits.rbegin(), digits.rend());
        return digits[0] * digits[1];
    }
};

class maxProduct {
    public int maxProduct(int n) {
        String s = Integer.toString(n);
        if(s.length() < 2) return 0;
        int[] digits = new int[s.length()];
        for(int i=0; ilength(); i++){
            digits[i] = s.charAt(i) - '0';
        }
        Arrays.sort(digits);
        int len = digits.length;
        return digits[len-1] * digits[len-2];
    }
}

class maxProduct:
    def maxProduct(self, n: int) -> int:
        digits = list(map(int, str(n)))
        if len(digits) < 2:
            return 0
        digits.sort(reverse=True)
        return digits[0] * digits[1]

Edge Cases and Special Considerations

Key edge cases to consider when implementing your solution:

1. Single Digit Input

Input: 5 → Output: 0
Explanation: Not enough digits to form product

2. Multiple Zeros

Input: 100 → Output: 0
Explanation: Best product is 1 × 0 = 0

3. All Same Digits

Input: 999 → Output: 81
Explanation: 9 × 9 = 81

Frequently Asked Questions