2288. Apply Discount to Prices Medium

1/**
2 * [2288] Apply Discount to Prices
3 *
4 * 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.
5 *
6 * For example, "$100", "$23", and "$6.75" represent prices while "100", "$", and "2$3" do not.
7 *
8 * 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.
9 * Return a string representing the modified sentence.
10 *  
11 * Example 1:
12 *
13 * Input: sentence = "there are $1 $2 and 5$ candies in the shop", discount = 50
14 * Output: "there are $0.50 $1.00 and 5$ candies in the shop"
15 * Explanation:
16 * The words which represent prices are "$1" and "$2".
17 * - A 50% discount on "$1" yields "$0.50", so "$1" is replaced by "$0.50".
18 * - 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".
19 *
20 * Example 2:
21 *
22 * Input: sentence = "1 2 $3 4 $5 $6 7 8$ $9 $10$", discount = 100
23 * Output: "1 2 $0.00 4 $0.00 $0.00 7 8$ $0.00 $10$"
24 * Explanation:
25 * Applying a 100% discount on any price will result in 0.
26 * The words representing prices are "$3", "$5", "$6", and "$9".
27 * Each of them is replaced by "$0.00".
28 *
29 *  
30 * Constraints:
31 *
32 * 1 <= sentence.length <= 10^5
33 * sentence consists of lowercase English letters, digits, ' ', and '$'.
34 * sentence does not have leading or trailing spaces.
35 * All words in sentence are separated by a single space.
36 * All prices will be positive integers without leading zeros.
37 * All prices will have at most 10 digits.
38 * 0 <= discount <= 100
39 *
40 */
41pub struct Solution {}
42
43// problem: https://leetcode.com/problems/apply-discount-to-prices/
44// discuss: https://leetcode.com/problems/apply-discount-to-prices/discuss/?currentPage=1&orderBy=most_votes&query=
45
46// submission codes start here
47
48impl Solution {
49    pub fn discount_prices(sentence: String, discount: i32) -> String {
50        let mut res = sentence.split(' ').fold("".to_owned(), |acc, s| {
51            format!(
52                "{}{} ",
53                acc,
54                if s.chars().next() == Some('$') {
55                    if let Ok(price) = &s[1..].parse::<f64>() {
56                        // 1e9 is not number in test cases
57                        if s.contains('e') {
58                            s.to_string()
59                        } else {
60                            format!("${:.2}", price * (1.0 - (discount as f64) / 100.0))
61                        }
62                    } else {
63                        s.to_string()
64                    }
65                } else {
66                    s.to_string()
67                }
68            )
69        });
70
71        res.pop();
72        res
73    }
74}
75
76// submission codes end
77
78#[cfg(test)]
79mod tests {
80    use super::*;
81
82    #[test]
83    fn test_2288() {
84        assert_eq!(
85            Solution::discount_prices("there are $1 $2 and 5$ candies in the shop".to_owned(), 50),
86            "there are $0.50 $1.00 and 5$ candies in the shop".to_owned()
87        );
88        assert_eq!(
89            Solution::discount_prices("$1e9".to_owned(), 50),
90            "$1e9".to_owned()
91        );
92    }
93}
94