976. Largest Perimeter Triangle

Problem

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

Example 2:

Input: nums = [1,2,1]
Output: 0

  Constraints:

• 3 <= nums.length <= 10^4

• 1 <= nums[i] <= 10^6

Solution (Java)

class Solution {
    public int largestPerimeter(int[] nums) {
        // for non zero area of triangle (c < a+b)
        Arrays.sort(nums);
        for (int i = nums.length - 1; i >= 2; i--) {
            if (nums[i] < nums[i - 1] + nums[i - 2]) {
                return nums[i] + nums[i - 1] + nums[i - 2];
            }
        }
        return 0;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).