LeetCode 1796: Second Largest Digit in a String Solution

Master LeetCode problem 1796 (Second Largest Digit in a String), a easy challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

1796. Second Largest Digit in a String

Easy

Hash Table String

Problem Explanation

Explanation

To solve this problem, we can iterate through the given string s and keep track of the unique numerical digits we encounter. We can store these digits in a set to ensure uniqueness. Once we have all unique digits, we can sort them in descending order and return the second largest digit if it exists.

Time complexity: O(n) where n is the length of the input string s.
Space complexity: O(1) since we are using a set to store at most 10 unique digits.

Solution Code

class Solution {
    public int secondHighest(String s) {
        Set<Integer> digits = new HashSet<>();
        
        for (char c : s.toCharArray()) {
            if (Character.isDigit(c)) {
                digits.add(Character.getNumericValue(c));
            }
        }
        
        List<Integer> sortedDigits = new ArrayList<>(digits);
        Collections.sort(sortedDigits, Collections.reverseOrder());
        
        if (sortedDigits.size() < 2) {
            return -1;
        }
        
        return sortedDigits.get(1);
    }
}

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