2024-02-15 Daily Challenge

Posted on:
Posted modified:
In: DailyChallenge

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

February LeetCoding Challenge 15

Description

Find Polygon With the Largest Perimeter

You are given an array of positive integers nums of length n.

A polygon is a closed plane figure that has at least 3 sides. The longest side of a polygon is smaller than the sum of its other sides.

Conversely, if you have k (k >= 3) positive real numbers a1, a2, a3, ..., ak where a1 <= a2 <= a3 <= ... <= ak and a1 + a2 + a3 + ... + ak-1 > ak, then there always exists a polygon with k sides whose lengths are a1, a2, a3, ..., ak.

The perimeter of a polygon is the sum of lengths of its sides.

Return the largest possible perimeter of a polygon whose sides can be formed from nums, or -1 if it is not possible to create a polygon.

 

Example 1:

Input: nums = [5,5,5]
Output: 15
Explanation: The only possible polygon that can be made from nums has 3 sides: 5, 5, and 5. The perimeter is 5 + 5 + 5 = 15.

Example 2:

Input: nums = [1,12,1,2,5,50,3]
Output: 12
Explanation: The polygon with the largest perimeter which can be made from nums has 5 sides: 1, 1, 2, 3, and 5. The perimeter is 1 + 1 + 2 + 3 + 5 = 12.
We cannot have a polygon with either 12 or 50 as the longest side because it is not possible to include 2 or more smaller sides that have a greater sum than either of them.
It can be shown that the largest possible perimeter is 12.

Example 3:

Input: nums = [5,5,50]
Output: -1
Explanation: There is no possible way to form a polygon from nums, as a polygon has at least 3 sides and 50 > 5 + 5.

 

Constraints:

  • 3 <= n <= 105
  • 1 <= nums[i] <= 109

Solution

class Solution {
public:
  long long largestPerimeter(vector<int>& nums) {
    sort(nums.begin(), nums.end());
    long long answer = 0;
    for(auto i : nums) {
      answer += i;
    }
    for(auto it = nums.rbegin(); it != nums.rend(); ++it) {
      if(*it * 2 >= answer) {
        answer -= *it;
      } else {
        break;
      }
    }
    if(answer <= nums[0] + nums[1]) return -1;
    return answer;
  }
};

// Accepted
// 980/980 cases passed (133 ms)
// Your runtime beats 90.42 % of cpp submissions
// Your memory usage beats 36.11 % of cpp submissions (83.3 MB)
Algorithm