[daily 3 questions (1)] the second largest number in the string

subject ：

Here's a mixed string  s , Please return s  in Second largest The number of , If there is no second largest number , Please return -1 .

Mixed string It's made up of small letters and numbers .

Example 1：

Input ：s = “dfa12321afd”
Output ：2
explain ： Appear in the s The numbers in include [1, 2, 3] . The second largest number is 2 .
Example 2：

Input ：s = “abc1111”
Output ：-1
explain ： Appear in the s The number in contains only [1] . There is no second largest number .

Tips ：

1 <= s.length <= 500
s  Only lowercase letters and （ or ） Numbers .

Ideas ：

This question is relatively simple , Direct traversal , Use two variables to record the 1 And the first 2 A large number is enough .

java Code ：

class Solution {
    public int secondHighest(String s) {
        int firstMax = -1;
        int secondMax = -1;

        for(int i=0;i<s.length();i++) {
            char ch = s.charAt(i);
            if('0'<=ch && ch<='9') {
                int num = ch-'0';
                if(firstMax<num) {
                    secondMax = firstMax;
                    firstMax = num;
                }else if(firstMax>num && secondMax<num) {
                    secondMax = num;
                }
            }
        }
        return secondMax;

    }
}