881. Boats to Save People

881. Boats to Save People

Medium

You are given an array people wherepeople[i] is the weight of the i^th person, and an infinite number of boats where each boat can carry a maximum weight of limit. Each boat carries at most two people at the same time, provided the sum of the weight of those people is at most limit.

Return the minimum number of boats to carry every given person.

Example 1:

• Input: people = [1,2], limit = 3
• Output: 1
• Explanation: 1 boat (1, 2)

Example 2:

• Input: people = [3,2,2,1], limit = 3
• Output: 3
• Explanation: 3 boats (1, 2), (2) and (3)

Example 3:

• Input: people = [3,5,3,4], limit = 5
• Output: 4
• Explanation: 4 boats (3), (3), (4), (5)

Constraints:

• 1 <= people.length <= 5 * 104
• 1 <= people[i] <= limit <= 3 * 104

Solution:

class Solution {

    /**
     * @param Integer[] $people
     * @param Integer $limit
     * @return Integer
     */
    function numRescueBoats($people, $limit) {
        $ans = 0;
        $i = 0;
        $j = count($people) - 1;

        sort($people);

        while ($i <= $j) {
            $remain = $limit - $people[$j];
            $j -= 1;
            if ($people[$i] <= $remain) {
                $i += 1;
            }
            $ans += 1;
        }

        return $ans;
    }
}

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