2678. Number of Senior Citizens

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.*

  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.

Solution

/**
 * @param {string[]} details
 * @return {number}
 */
var countSeniors = function(details) {
    var count = 0;
    for (var i = 0; i < details.length; i++) {
        if (details[i][11] > '6' || (details[i][11] === '6' && details[i][12] > '0')) {
            count += 1;
        }
    }
    return count;
};

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(1).