LeetCode 2971: Find Polygon With the Largest Perimeter Solution

Master LeetCode problem 2971 (Find Polygon With the Largest Perimeter), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

2971. Find Polygon With the Largest Perimeter

Medium

Array Greedy Sorting Prefix Sum

Problem Explanation

Explanation

To find the largest possible perimeter of a polygon that can be formed using sides from the given array nums, we need to consider the largest sides first in order to maximize the perimeter. We can achieve this by sorting the array in descending order and then iterating over the sorted array to check if any set of consecutive sides can form a valid polygon.

Algorithm:

Sort the input array nums in descending order.
Iterate over the sorted array from index 0 to n-3 (to have at least 3 sides to form a polygon).
Check if the current triplet of sides can form a valid polygon (largest side < sum of other two sides).
If a valid polygon can be formed, return the perimeter.
If no valid polygon can be formed, return -1.

Time Complexity: O(n log n) for sorting the array, where n is the number of elements in the input array. Space Complexity: O(1) as we are using constant extra space for variables.

Solution Code

import java.util.Arrays;

class Solution {
    public int largestPerimeter(int[] nums) {
        Arrays.sort(nums);
        for (int i = nums.length - 3; i >= 0; i--) {
            if (nums[i] + nums[i + 1] > nums[i + 2]) {
                return nums[i] + nums[i + 1] + nums[i + 2];
            }
        }
        return -1;
    }
}

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