LeetCode 2288. Apply Discount to Prices Solution in Java, C++, Python & More | Explanation + Code

Description

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 sequence of digits preceded by a dollar sign.

• For example, "100", "23", and "6" represent prices while "100", "", and "$1e5" 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.

Note that all prices will contain at most 10 digits.

 

Example 1:

Input: sentence = "there are 12 and 5$ candies in the shop", discount = 50
Output: "there are 0.501.00 and 5$ candies in the shop"
Explanation: 
The words which represent prices are "1" and "2". 
- A 50% discount on "1" yields "0.50", so "1" is replaced by "0.50".
- A 50% discount on "2" yields "1". Since we need to have exactly 2 decimal places after a price, we replace "2" with "1.00".

Example 2:

Input: sentence = "1 2 3 45 6 7 8 910$", discount = 100
Output: "1 2 0.00 40.00 0.00 7 8 0.0010$"
Explanation: 
Applying a 100% discount on any price will result in 0.
The words representing prices are "3", "5", "6", and "9".
Each of them is replaced by "$0.00".

 

Constraints:

• 1 <= sentence.length <= 105
• sentence consists of lowercase English letters, digits, ' ', and '$'.
• sentence does not have leading or trailing spaces.
• All words in sentence are separated by a single space.
• All prices will be positive numbers without leading zeros.
• All prices will have at most 10 digits.
• 0 <= discount <= 100

Solutions

Solution 1: Simulation

We can split the sentence into an array of words by spaces, then iterate through the array of words. For each word, if it represents a price, we update it to the price after applying the discount. Finally, we concatenate the updated array of words into a space-separated string.

The time complexity is O(n), and the space complexity is O(n). Here, n is the length of the string sentence.

PythonJavaC++GoTypeScript

class Solution: def discountPrices(self, sentence: str, discount: int) -> str: ans = [] for w in sentence.split(): if w[0] == '$' and w[1:].isdigit(): w = f'${int(w[1:]) * (1 - discount / 100):.2f}' ans.append(w) return ' '.join(ans)(code-box)

class Solution { public String discountPrices(String sentence, int discount) { String[] words = sentence.split(" "); for (int i = 0; i < words.length; ++i) { if (check(words[i])) { double t = Long.parseLong(words[i].substring(1)) * (1 - discount / 100.0); words[i] = String.format("$%.2f", t); } } return String.join(" ", words); } private boolean check(String s) { if (s.charAt(0) != '$' || s.length() == 1) { return false; } for (int i = 1; i < s.length(); ++i) { if (!Character.isDigit(s.charAt(i))) { return false; } } return true; } }(code-box)

class Solution { public: string discountPrices(string sentence, int discount) { istringstream is(sentence); string w; string ans; auto check = [](string s) { if (s[0] != '$' || s.size() == 1) { return false; } for (int i = 1; i < s.size(); ++i) { if (!isdigit(s[i])) { return false; } } return true; }; while (is >> w) { if (check(w)) { long long v = stoll(w.substr(1)) * (100 - discount); char t[20]; sprintf(t, "$%lld.%02lld", v / 100, v % 100); ans += t; } else { ans += w; } ans += ' '; } ans.pop_back(); return ans; } };(code-box)

func discountPrices(sentence string, discount int) string { words := strings.Split(sentence, " ") for i, w := range words { if w[0] == '$' { if v, err := strconv.Atoi(w[1:]); err == nil { words[i] = fmt.Sprintf("$%.2f", float64(v*(100-discount))/100) } } } return strings.Join(words, " ") }(code-box)

function discountPrices(sentence: string, discount: number): string { const sell = (100 - discount) / 100; const reg = new RegExp(/^(\$)(([1-9]\d*\.?\d*)|(0\.\d*))$/g); const words = sentence.split(' ').map(d => { if (!reg.test(d)) return d; return d.replace(reg, (s, $1, $2) => { return `$${(sell * $2).toFixed(2)}`; }); }); return words.join(' '); }(code-box)