LeetCode 2678. Number of Senior Citizens Solution in Java, C++, Python & More | Explanation + Code

Description

You are given a 0-indexed array of strings details. Each element of details provides information about a given passenger compressed into a string of length 15. The system is such that:

• The first ten characters consist of the phone number of passengers.
• The next character denotes the gender of the person.
• The following two characters are used to indicate the age of the person.
• The last two characters determine the seat allotted to that person.

Return the number of passengers who are strictly more than 60 years old.

 

Example 1:

Input: details = ["7868190130M7522","5303914400F9211","9273338290F4010"]
Output: 2
Explanation: The passengers at indices 0, 1, and 2 have ages 75, 92, and 40. Thus, there are 2 people who are over 60 years old.

Example 2:

Input: details = ["1313579440F2036","2921522980M5644"]
Output: 0
Explanation: None of the passengers are older than 60.

 

Constraints:

• 1 <= details.length <= 100
• details[i].length == 15
• details[i] consists of digits from '0' to '9'.
• details[i][10] is either 'M' or 'F' or 'O'.
• The phone numbers and seat numbers of the passengers are distinct.

Solutions

Solution 1: Traversal and Counting

We can traverse each string x in details and convert the 12th and 13th characters (indexed at 11 and 12) of x to integers, and check if they are greater than 60. If so, we add one to the answer.

After the traversal, we return the answer.

The time complexity is O(n), where n is the length of details. The space complexity is $O(1)`.

PythonJavaC++GoTypeScriptRust

class Solution: def countSeniors(self, details: List[str]) -> int: return sum(int(x[11:13]) > 60 for x in details)(code-box)

class Solution { public int countSeniors(String[] details) { int ans = 0; for (var x : details) { int age = Integer.parseInt(x.substring(11, 13)); if (age > 60) { ++ans; } } return ans; } }(code-box)

class Solution { public: int countSeniors(vector<string>& details) { int ans = 0; for (auto& x : details) { int age = stoi(x.substr(11, 2)); ans += age > 60; } return ans; } };(code-box)

func countSeniors(details []string) (ans int) { for _, x := range details { age, _ := strconv.Atoi(x[11:13]) if age > 60 { ans++ } } return }(code-box)

function countSeniors(details: string[]): number { return details.filter(x => +x.slice(11, 13) > 60).length; }(code-box)

impl Solution { pub fn count_seniors(details: Vec<String>) -> i32 { details .iter() .filter_map(|s| s[11..13].parse::<i32>().ok()) .filter(|&age| age > 60) .count() as i32 } }(code-box)