Boats to Save People

Sort the people by weight. For each unboarded heaviest person, scan through the remaining people to find the heaviest one that can share their boat.

1. 1Sort people.
2. 2Track who has been boarded using a boolean array.
3. 3For each unboarded person from the heaviest, scan forward for the heaviest person that fits.
4. 4Increment boat count each time.

Why it's not optimal: The inner scan is O(n), making the whole approach O(n²). Two pointers achieves the same greedy pairing in O(n) after sorting.

def numRescueBoats(people, limit):
    people.sort()
    boarded = [False] * len(people)
    boats = 0
    for i in range(len(people) - 1, -1, -1):
        if boarded[i]: continue
        boarded[i] = True
        for j in range(0, i):
            if not boarded[j] and people[i] + people[j] <= limit:
                boarded[j] = True; break
        boats += 1
    return boats

After sorting, use two pointers at both ends. The heaviest person always takes a boat. If they can share with the lightest remaining person (sum ≤ limit), pair them. Otherwise the heaviest goes alone. Either way, one boat is used and we move R left.

1. 1Sort people. Set L=0, R=n-1, boats=0.
2. 2While L <= R: if people[L] + people[R] <= limit, both board — L++.
3. 3Always decrement R and increment boats.