// 2971. Find Polygon With the Largest Perimeter #include "leetcode.h" /* * given an arry 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 then there always exists a polygon with 'k' sides * whose lengths are 'a1,a2,...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. */ int cmp(const void *a, const void *b) { return *(int *)b - *(int *)a; } long long largestPerimeter(int *nums, int nums_size) { long long ans = -1, sums[nums_size - 1]; qsort(nums, nums_size, sizeof(int), cmp); sums[nums_size - 2] = nums[nums_size - 2] + nums[nums_size - 1]; for (int i = nums_size - 3; i >= 0; i--) { sums[i] = nums[i] + sums[i + 1]; if (nums[i] < sums[i + 1]) ans = sums[i]; } return ans; } int main() { int n1[] = {5, 5, 5}, n2[] = {1, 12, 1, 2, 5, 50, 3}, n3[] = {5, 5, 50}; printf("%lld\n", largestPerimeter(n1, ARRAY_SIZE(n1))); // expect: 15 printf("%lld\n", largestPerimeter(n2, ARRAY_SIZE(n2))); // expect: 12 printf("%lld\n", largestPerimeter(n3, ARRAY_SIZE(n3))); // expect: -1 }