From 15d736376916c6d58a6b4d47b0e9fa819d756350 Mon Sep 17 00:00:00 2001
From: VicRen <vic.ren@me.com>
Date: Sat, 31 Oct 2020 23:01:57 +0800
Subject: [PATCH] 31: coin sums

---
 31_coin_sums/main.go      | 20 +++++++++++++++++++
 31_coin_sums/main_test.go | 42 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+)
 create mode 100644 31_coin_sums/main.go
 create mode 100644 31_coin_sums/main_test.go

diff --git a/31_coin_sums/main.go b/31_coin_sums/main.go
new file mode 100644
index 0000000..d9491ce
--- /dev/null
+++ b/31_coin_sums/main.go
@@ -0,0 +1,20 @@
+package main
+
+import "fmt"
+
+var coins = []int{1, 2, 5, 10, 20, 50, 100, 200}
+
+func main() {
+	fmt.Println(sumCoins(200))
+}
+
+func sumCoins(target int) int {
+	t := make([]int, target+1)
+	t[0] = 1
+	for _, c := range coins {
+		for j := c; j <= target; j++ {
+			t[j] += t[j-c]
+		}
+	}
+	return t[target]
+}
diff --git a/31_coin_sums/main_test.go b/31_coin_sums/main_test.go
new file mode 100644
index 0000000..1fd4b29
--- /dev/null
+++ b/31_coin_sums/main_test.go
@@ -0,0 +1,42 @@
+package main
+
+import "testing"
+
+func Test_sumCoins(t *testing.T) {
+	type args struct {
+		target int
+	}
+	tt := []struct {
+		name string
+		args args
+		want int
+	}{
+		{
+			"1",
+			args{1},
+			1,
+		},
+		{
+			"2",
+			args{2},
+			2,
+		},
+		{
+			"3",
+			args{3},
+			2,
+		},
+		{
+			"4",
+			args{4},
+			3,
+		},
+	}
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := sumCoins(tc.args.target); got != tc.want {
+				t.Errorf("sumCoins() = %v, want %v", got, tc.want)
+			}
+		})
+	}
+}