largest perimeter triangle

largestperimeter/largestperimeter.go

@@ -0,0 +1,27 @@
+package largestperimeter
+
+import (
+	"sort"
+)
+
+func isTriangle(a, b, c int) bool {
+	return a < b+c
+}
+
+func largestPerimeter(nums []int) int {
+
+	sort.Ints(nums)
+
+	for i := len(nums) - 1; i >= 2; i-- {
+		a, b, c := nums[i], nums[i-1], nums[i-2]
+		if isTriangle(a, b, c) {
+			return a + b + c
+		}
+	}
+
+	return 0
+}
+
+func Triangle(nums []int) int {
+	return largestPerimeter(nums)
+}

largestperimeter/largestperimeter_test.go

@@ -0,0 +1,28 @@
+package largestperimeter_test
+
+import (
+	"testing"
+
+	"git.jxs.me/leetgo/largestperimeter"
+	"github.com/stretchr/testify/require"
+)
+
+func TestEmpty(t *testing.T) {
+	require.Equal(t, 0, largestperimeter.Triangle([]int{}))
+}
+
+func TestTooSmall(t *testing.T) {
+	require.Equal(t, 0, largestperimeter.Triangle([]int{1, 2}))
+}
+
+func TestWorking(t *testing.T) {
+	require.Equal(t, 5, largestperimeter.Triangle([]int{2, 1, 2}))
+}
+
+func TestInvalid(t *testing.T) {
+	require.Equal(t, 0, largestperimeter.Triangle([]int{2, 1, 1}))
+}
+
+func TestHundredSize(t *testing.T) {
+	require.Equal(t, 118, largestperimeter.Triangle([]int{100, 49, 50, 7, 19}))
+}

largestperimeter/readme.md

@@ -0,0 +1,23 @@
+976. Largest Perimeter Triangle
+Easy
+
+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 <= 104
+    1 <= nums[i] <= 106