Add 2015 Day 20 solutions

4 files changed, 72 insertions, 0 deletions

diff --git a/2015/20/.gitignore b/2015/20/.gitignore
new file mode 100644
index 0000000..60d075d
--- /dev/null
+++ b/2015/20/.gitignore
@@ -0,0 +1 @@
+puzzle-[12]
diff --git a/2015/20/Makefile b/2015/20/Makefile
new file mode 100644
index 0000000..8d1d1fa
--- /dev/null
+++ b/2015/20/Makefile
@@ -0,0 +1,12 @@
+all:
+	sed '/START PART 2/,/END PART 2/d' puzzles.go >tmp1.go
+	sed '/START PART 1/,/END PART 1/d' puzzles.go >tmp2.go
+	go build tmp1.go
+	go build tmp2.go
+	mv tmp1 puzzle-1
+	mv tmp2 puzzle-2
+	rm -f tmp[12].go
+
+.PHONY: clean
+clean:
+	rm -f puzzle-[12]
diff --git a/2015/20/input b/2015/20/input
new file mode 100644
index 0000000..282bc62
--- /dev/null
+++ b/2015/20/input
@@ -0,0 +1 @@
+33100000
diff --git a/2015/20/puzzles.go b/2015/20/puzzles.go
new file mode 100644
index 0000000..5f2d37f
--- /dev/null
+++ b/2015/20/puzzles.go
@@ -0,0 +1,58 @@
+package main
+
+import (
+	"fmt"
+	"math"
+	"os"
+)
+
+func calc(n int) int {
+	acc := 0
+	s := math.Sqrt(float64(n))
+
+	if s == math.Trunc(s) {
+		acc += int(s)
+	} else {
+		s = math.Ceil(s)
+	}
+
+	for i := 1; i < int(s); i++ {
+		if n % i == 0 {
+			/* START PART 2 */
+			ndi := n / i
+			if ndi <= 50 {
+				acc += i + ndi
+			} else if i <= 50 {
+				acc += ndi
+			}
+			/* END PART 2 START PART 1 */
+			acc += i + n / i
+			/* END PART 1 */
+		}
+	}
+
+	return acc
+}
+
+func main() {
+	file, err := os.Open("input")
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%s: %s\n", os.Args[0], err)
+		os.Exit(1)
+	}
+
+	var n int
+	fmt.Fscanf(file, "%d", &n)
+	/* START PART 2 */
+	sn := n / 11
+	/* END PART 2 START PART 1 */
+	sn := n / 10
+	/* END PART 1 */
+
+	for i := 1; i <= n; i++ {
+		if calc(i) >= sn {
+			fmt.Println(i)
+			break
+		}
+	}
+}