2678. Number of Senior Citizens

2678. Number of Senior Citizens

Easy

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.

Hint:

1. Convert the value at index 11 and 12 to a numerical value.
2. The age of the person at index i is equal to details[i][11]*10+details[i][12].

Solution:

To solve this problem, we can follow these steps:

1. Extract the Age: The age is located at the 12th and 13th positions in each string.
2. Convert to Integer: Convert the extracted age substring to an integer.
3. Count Senior Citizens: Count how many of these ages are strictly greater than 60.

Let's implement this solution in PHP: 2678. Number of Senior Citizens

<?php
// Example usage:
$details1 = ["7868190130M7522","5303914400F9211","9273338290F4010"];
$details2 = ["1313579440F2036","2921522980M5644"];

echo countSeniorCitizens($details1); // Output: 2
echo countSeniorCitizens($details2); // Output: 0

?>

Explanation:

1. Function Definition: The function countSeniorCitizens takes an array of strings details as input.
2. Initialize Counter: We initialize a counter $seniorCount to keep track of the number of senior citizens.
3. Loop Through Each Detail: We loop through each element in the details array.
4. Extract Age: For each detail string, we extract the substring from index 11 to 12 (2 characters) and convert it to an integer using intval.
5. Check Age Condition: We check if the extracted age is strictly greater than 60.
6. Increment Counter: If the condition is true, we increment the $seniorCount.
7. Return Count: After looping through all the details, we return the count of senior citizens.

Testing:

• For the input ["7868190130M7522","5303914400F9211","9273338290F4010"], the output is 2 because the ages are 75, 92, and 40, with 75 and 92 being greater than 60.
• For the input ["1313579440F2036","2921522980M5644"], the output is 0 because the ages are 20 and 56, neither of which are greater than 60.

This solution is efficient and straightforward, working within the constraints provided.

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