Leetcode: Boats to Save People

Boats to Save People



Similar Problems:


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. 1 <= people.length <= 50000
  2. 1 <= people[i] <= limit <= 30000

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.


  • Solution:
// Blog link: https://code.dennyzhang.com/boats-to-save-people
// Basic Ideas: greedy + two-sum-close
//
// Complexity: Time O(n*log(n)), Space O(1)
import (
    "sort"
)
func numRescueBoats(people []int, limit int) int {
    sort.Ints(people)
    res := 0
    l, r := 0, len(people)-1
    for l<=r {
        v := people[l]+people[r]
        if v <= limit {
            l, r = l+1, r-1
        } else {
            r -= 1
        }
        res++
    }
    return res
}
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