1796

1796. Second Largest Digit in a String (Easy)

Given an alphanumeric string s, return the second largest numerical digit that appears in s, or -1 if it does not exist.

An alphanumeric string is a string consisting of lowercase English letters and digits.

 

Example 1:

Input: s = "dfa12321afd"
Output: 2
Explanation: The digits that appear in s are [1, 2, 3]. The second largest digit is 2.

Example 2:

Input: s = "abc1111"
Output: -1
Explanation: The digits that appear in s are [1]. There is no second largest digit. 

 

Constraints:

• 1 <= s.length <= 500
• s consists of only lowercase English letters and/or digits.

Related Topics:
String

Solution 1.

// OJ: https://leetcode.com/problems/second-largest-digit-in-a-string
// Author: github.com/lzl124631x
// Time: O(N)
// Space: O(1)
class Solution {
public:
    int secondHighest(string s) {
        set<int> st;
        for (char c : s) {
            if (isdigit(c)) st.insert(c - '0');
        }
        if (st.size() < 2) return -1;
        return *next(st.rbegin());
    }
};