From f4a18fb4ed80e03b3595b17edb90af39be9e1b2e Mon Sep 17 00:00:00 2001
From: VicRen <vic.ren@me.com>
Date: Tue, 10 Nov 2020 08:55:35 +0800
Subject: [PATCH] 39: integer right triangles

---
 39_integer_right_triangles/main.go      | 34 +++++++++++++++++++++++++
 39_integer_right_triangles/main_test.go | 30 ++++++++++++++++++++++
 2 files changed, 64 insertions(+)
 create mode 100644 39_integer_right_triangles/main.go
 create mode 100644 39_integer_right_triangles/main_test.go

diff --git a/39_integer_right_triangles/main.go b/39_integer_right_triangles/main.go
new file mode 100644
index 0000000..cc42ce2
--- /dev/null
+++ b/39_integer_right_triangles/main.go
@@ -0,0 +1,34 @@
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+func main() {
+	max := 0
+	fp := 0
+	for p := 0; p <= 1000; p++ {
+		n := len(findSolutionsFor(p))
+		if n > max {
+			max = n
+			fp = p
+		}
+	}
+	fmt.Println("max:", max, "fp", fp)
+}
+
+func findSolutionsFor(p int) [][]int {
+	// a+b+c=p, a^2+b^2=c^2, a+b>c, c>a, c>b
+	var ret [][]int
+	for a := 0; a < p/2; a++ {
+		for b := 0; b < a; b++ {
+			cf := math.Sqrt(float64(a*a + b*b))
+			c := int(cf)
+			if cf-float64(c) == 0 && a+b+c == p {
+				ret = append(ret, []int{b, a, c})
+			}
+		}
+	}
+	return ret
+}
diff --git a/39_integer_right_triangles/main_test.go b/39_integer_right_triangles/main_test.go
new file mode 100644
index 0000000..4a9795d
--- /dev/null
+++ b/39_integer_right_triangles/main_test.go
@@ -0,0 +1,30 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func Test_findSolutionsFor(t *testing.T) {
+	type args struct {
+		n int
+	}
+	tests := []struct {
+		name string
+		args args
+		want [][]int
+	}{
+		{
+			"120",
+			args{120},
+			[][]int{{30, 40, 50}, {24, 45, 51}, {20, 48, 52}},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := findSolutionsFor(tt.args.n); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("findSolutionsFor() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}