812 finish

Author: aQua

Algorithms/0812.largest-triangle-area/largest-triangle-area.go

@@ -1,6 +1,32 @@
 package problem0812
 
 func largestTriangleArea(points [][]int) float64 {
-    
-	return 0
+	maxArea := 0.0
+	n := len(points)
+	for i := 0; i < n; i++ {
+		for j := i + 1; j < n; j++ {
+			for k := j + 1; k < n; k++ {
+				maxArea = max(maxArea, area(points[i], points[j], points[k]))
+			}
+		}
+	}
+	return maxArea
+}
+
+func area(p1, p2, p3 []int) float64 {
+	return abs(p1[0]*p2[1]+p2[0]*p3[1]+p3[0]*p1[1]-p1[0]*p3[1]-p2[0]*p1[1]-p3[0]*p2[1]) / 2
+}
+
+func abs(num int) float64 {
+	if num < 0 {
+		num = -num
+	}
+	return float64(num)
+}
+
+func max(a, b float64) float64 {
+	if a > b {
+		return a
+	}
+	return b
 }