881. Boats to Save People

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# 題目敘述

You are given an array people where people[i] is the weight of the ith 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)

# 解題思路

# Solution

import java.util.Arrays;

class Solution {

    public int numRescueBoats(int[] people, int limit) {

        Arrays.sort(people);

        int ans = 0;

        int left = 0, right = people.length - 1;

        while (left <= right) {

            if (people[left] + people[right--] <= limit) {

                left++;

            }

            ans++;

        }

        return ans;

    }

}

#include <vector>

#include <algorithm>

using namespace std;

class Solution {

public:

    int numRescueBoats(vector<int>& people, int limit) {

        sort(people.begin(), people.end());

        int ans = 0;

        int left = 0, right = people.size() - 1;

        while (left <= right) {

            if (people[left] + people[right--] <= limit) {

                left++;

            }

            ans++;

        }

        return ans;

    }

};