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Formatted question description: https://leetcode.ca/all/1796.html

1796. Second Largest Digit in a String

Level

Easy

Description

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.

Solution

Loop over s and count the occurrences of all digits. Then loop over all digits backwards and find the second largest digit that has occurrence greater than 0. If such a digit exists, return the digit. Otherwise, return -1.

  • class Solution {
    public int secondHighest(String s) {
        int[] counts = new int[10];
        int length = s.length();
        for (int i = 0; i < length; i++) {
            char c = s.charAt(i);
            if (c >= '0' && c <= '9')
                counts[c - '0']++;
        }
        boolean flag = false;
        for (int i = 9; i >= 0; i--) {
            if (counts[i] > 0) {
                if (!flag)
                    flag = true;
                else
                    return i;
            }
        }
        return -1;
    }
}

  • // OJ: https://leetcode.com/problems/second-largest-digit-in-a-string
// 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());
    }
};

  • class Solution:
    def secondHighest(self, s: str) -> int:
        a = b = -1
        for c in s:
            if c.isdigit():
                v = int(c)
                if v > a:
                    a, b = v, a
                elif b < v < a:
                    b = v
        return b

############

# 1796. Second Largest Digit in a String
# https://leetcode.com/problems/second-largest-digit-in-a-string

class Solution:
    def secondHighest(self, s: str) -> int:
        res = set(list(c for c in s if c.isdigit()))
    
        return sorted(list(res))[-2] if len(res) > 1 else -1

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