## DEV Community

MD ARIFUL HAQUE

Posted on • Updated on

# 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.