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

September LeetCoding Challenge 28

Description

Largest Perimeter Triangle

Given an integer array nums, return the largest perimeter of a triangle with a non-zero area, formed from three of these lengths. If it is impossible to form any triangle of a non-zero area, return 0.

Example 1:

Input: nums = [2,1,2]
Output: 5
Explanation: You can form a triangle with three side lengths: 1, 2, and 2.

Example 2:

Input: nums = [1,2,1,10]
Output: 0
Explanation: 
You cannot use the side lengths 1, 1, and 2 to form a triangle.
You cannot use the side lengths 1, 1, and 10 to form a triangle.
You cannot use the side lengths 1, 2, and 10 to form a triangle.
As we cannot use any three side lengths to form a triangle of non-zero area, we return 0.

Constraints:

• 3 <= nums.length <= 104
• 1 <= nums[i] <= 106

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
public:
  int largestPerimeter(vector<int>& nums) {
    sort(nums.begin(), nums.end(), greater<int>());
    for(int i = 0; i < nums.size() - 2; ++i) {
      if(nums[i] - nums[i + 1] < nums[i + 2]) {
        return nums[i] + nums[i + 1] + nums[i + 2];
      }
    }
    return 0;
  }
};

// Accepted
// 84/84 cases passed (28 ms)
// Your runtime beats 99.7 % of cpp submissions
// Your memory usage beats 96.06 % of cpp submissions (21.7 MB)