Problem

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.

Examples

Example 1:

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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:

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

Solution

Method 1 - Use substring and Integer Parsing

Video Explanation

Here is the video explanation of the same:

Code

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class Solution {
    public int countSeniors(String[] details) {
        int count = 0;
        for(String detail: details) {
            int age = Integer.valueOf(detail.substring(11, 13));
            if (age > 60) {
                count++;
            }
        }
        return count;
    }
}

Complexity

  • ⏰ Time complexity: O(n), where n is number of elements in the array (Each ticket is of length 15, so O(15n) = O(n))
  • 🧺 Space complexity: O(1)