1796. Second Largest Digit in a String

class Solution {
public:
    int secondHighest(string s) 
    {
        string temp;

        for(int i=0; i<s.length(); i++)
        {
            if(s[i]>=48 && s[i]<=57)
                temp+=s[i];
        }
        int max = 0;
        for(int i=0; i<temp.length(); i++)
        {
            if((temp[i]-'0') > max)
               max = temp[i]-'0';
        }

        int secondMax=-1;
        for(int i=0; i<temp.length(); i++)
        {
            if(secondMax < (temp[i]-'0') && (temp[i]-'0') < max)
                 secondMax = temp[i]-'0';
        }
        return secondMax;
    }
};