Today I have done leetcode's April LeetCoding Challenge with cpp.

April LeetCoding Challenge 3

Description

Boats to Save People

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)

Constraints:

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

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
public:
  int numRescueBoats(vector<int>& people, int limit) {
    sort(people.begin(), people.end());
    int len = people.size();
    if(people.back() * 2 <= limit) return (len + 1) / 2;
    if(people.front() * 2 > limit) return len;
    int ed = len - 1;
    int st = 0;
    int answer = 0;
    while(st < ed) {
      if(people[st] + people[ed] > limit) {
        ed -= 1;
      } else {
        ed -= 1;
        st += 1;
      }
      answer += 1;
    }
    answer += (st == ed);
    return answer;
  }
};


// Accepted
// 78/78 cases passed (68 ms)
// Your runtime beats 97.18 % of cpp submissions
// Your memory usage beats 57.42 % of cpp submissions (42 MB)