From 23353c144ac9b158af7616dc46b636d53b73ce34 Mon Sep 17 00:00:00 2001 From: Jack Sangdahl Date: Thu, 25 Sep 2025 21:03:37 -0600 Subject: 611. valid triangle number --- valid_triangle_number.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) create mode 100644 valid_triangle_number.c (limited to 'valid_triangle_number.c') diff --git a/valid_triangle_number.c b/valid_triangle_number.c new file mode 100644 index 0000000..83585f7 --- /dev/null +++ b/valid_triangle_number.c @@ -0,0 +1,31 @@ +// 611. Valid Triangle Number +#include "leetcode.h" + +/* + * given an integer array 'nums', return the number of triplets chosen from the + * array that can make triangles if we take them as side lengths of a triangle + */ + +int cmp(const void *a, const void *b) { return (*(int *)a - *(int *)b); } + +int triangleNumber(int *nums, int numsSize) { + qsort(nums, numsSize, sizeof(int), cmp); + int ans = 0; + for (int k = 2; k < numsSize; ++k) { + int i = 0, j = k - 1; + while (i < j) { + if (nums[i] + nums[j] > nums[k]) { + ans += j - i; + j--; + } else + i++; + } + } + return ans; +} + +int main() { + int n1[] = {2, 2, 3, 4}, n2[] = {4, 2, 3, 4}; + printf("%d\n", triangleNumber(n1, ARRAY_SIZE(n1))); // expect: 3 + printf("%d\n", triangleNumber(n2, ARRAY_SIZE(n2))); // expect: 4 +} -- cgit v1.2.3