1881. Maximum Value after Insertion

You are given a very large integer n, represented as a string,​​​​​​ and an integer digit x. The digits in n and the digit x are in the inclusive range [1, 9], and n may represent a negative number.

You want to maximize n’s numerical value by inserting x anywhere in the decimal representation of n​​​​​​. You cannot insert x to the left of the negative sign.

• For example, if n = 73 and x = 6, it would be best to insert it between 7 and 3, making n = 763.
• If n = -55 and x = 2, it would be best to insert it before the first 5, making n = -255.

Return a string representing the maximum value of n​​​​​​ after the insertion.

class Solution {
    string findLessValue(string n, int x) {
        int pos = n.size();
        for(int i = 1; i < n.size(); i++) {
            if(n[i] - '0' > x) {pos = i; break; }
        }
        return n.substr(0,pos) + to_string(x ) + n.substr(pos);
    }
    
    string findGreaterValue(string n, int x) {
        int pos = n.size();
        for(int i = 0; i < n.size(); i++) {
            if(n[i] - '0' < x) {pos = i; break; }
        }
        return n.substr(0,pos) + to_string(x ) + n.substr(pos);
    }
public:
    string maxValue(string n, int x) {
        return n[0] == '-' ? findLessValue(n, x) : findGreaterValue(n, x);
    }
};