2288. Apply Discount to Prices

A sentence is a string of single-space separated words where each word can contain digits, lowercase letters, and the dollar sign ‘$’. A word represents a price if it is a non-negative real number preceded by a dollar sign.

• For example, “$100”, “$23”, and “$6.75” represent prices while “100”, “$”, and “2$3” do not.

You are given a string sentence representing a sentence and an integer discount. For each word representing a price, apply a discount of discount% on the price and update the word in the sentence. All updated prices should be represented with exactly two decimal places.

Return a string representing the modified sentence.

class Solution {
    string parse(string& s, int& i) {
        int n = s.length();
        string res = "";
        while(i < n and s[i] != ' ') {
            res.push_back(s[i++]);
        }
        return res;
    }
    bool isMoney(string& s) {
        if(s[0] != '$') return false;
        if(s.length() == 1) return false;
        bool dot = false;
        for(int i = 1; i < s.length(); i++) {
            if(s[i] == '.') {
                if(i + 1 == s.length()) return false;
                if(i == 1) return false;
                dot = true;
            } else if(!isdigit(s[i])) return false;
        }
        return true;
    }
    double toDobule(string& s) {
        return stod(s.substr(1)) + 1e-6;
    }
public:
    string discountPrices(string sentence, int discount) {
        int i = 0, n = sentence.length();
        string res = "";
        while(i < n) {
            string token = parse(sentence, i);
            if(isMoney(token)) {
                long double cost = toDobule(token);
                cost = cost - (cost * discount / 100);
                string money = "$" + to_string(cost);
                int cut = money.length();
                for(int i = 0; i < money.length(); i++) {
                    if(money[i] == '.') {
                        cut = i += 2;
                    }
                }
                string valid = money.substr(0, cut + 1);
                res += valid;
            } else res += token;
            if(i < n) {
                res.push_back(' '); i++;
            }
        }
        return res;
    }
};