# 881. Boats to Save People

The `i`-th person has weight `people[i]`, and each boat can carry a maximum weight of `limit`.

Each boat carries at most 2 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.  (It is guaranteed each person can be carried by a boat.)

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)
``````

Note:

• `1 <= people.length <= 50000`
• `1 <= people[i] <= limit <= 30000`

``````class Solution {
public:
int numRescueBoats(vector<int>& people, int limit) {
int res = 0, n = people.size(), left = 0, right = n - 1;
sort(people.begin(), people.end());
while (left <= right) {
if (people[left] + people[right] <= limit) ++left;
--right;
++res;
}
return res;
}
};
``````

Github 同步地址:

https://github.com/grandyang/leetcode/issues/881

https://leetcode.com/problems/boats-to-save-people/

https://leetcode.com/problems/boats-to-save-people/discuss/156740/C%2B%2BJavaPython-Two-Pointers

https://leetcode.com/problems/boats-to-save-people/discuss/156855/6-lines-Java-O(nlogn)-code-sorting-%2B-greedy-with-greedy-algorithm-proof.

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