From 0e9f5569d800b4188bb873474e3f488b2fc5c3f5 Mon Sep 17 00:00:00 2001
From: Vasko Zdravevski <vaskoz@users.noreply.github.com>
Date: Wed, 25 Dec 2019 21:43:18 -0700
Subject: [PATCH 1/2] day 289: can player one force a win. simple xor theorem

---
 day289/problem.go      | 13 +++++++++++++
 day289/problem_test.go | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)
 create mode 100644 day289/problem.go
 create mode 100644 day289/problem_test.go

diff --git a/day289/problem.go b/day289/problem.go
new file mode 100644
index 0000000..f18c801
--- /dev/null
+++ b/day289/problem.go
@@ -0,0 +1,13 @@
+package day289
+
+// CanFirstPlayerForceWinNimGame answers if the first player
+// can force a win with the given heap configuration.
+func CanFirstPlayerForceWinNimGame(heaps []int) bool {
+	sum := 0
+
+	for _, heap := range heaps {
+		sum ^= heap
+	}
+
+	return sum != 0
+}
diff --git a/day289/problem_test.go b/day289/problem_test.go
new file mode 100644
index 0000000..b57990a
--- /dev/null
+++ b/day289/problem_test.go
@@ -0,0 +1,35 @@
+package day289
+
+import "testing"
+
+// nolint
+var testcases = []struct {
+	heaps     []int
+	forcedWin bool
+}{
+	{[]int{3, 4, 5}, true},
+	{[]int{1, 2, 3}, false},
+	{[]int{1, 4, 5}, false},
+	{[]int{1, 6, 7}, false},
+	{[]int{5, 9, 12}, false},
+	{[]int{1, 2, 4, 7}, false},
+	{[]int{1, 2, 4, 6}, true},
+}
+
+func TestCanFirstPlayerForceWinNimGame(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range testcases {
+		if res := CanFirstPlayerForceWinNimGame(tc.heaps); res != tc.forcedWin {
+			t.Errorf("Expected %v, got %v", tc.forcedWin, res)
+		}
+	}
+}
+
+func BenchmarkCanFirstPlayerForceWinNimGame(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			CanFirstPlayerForceWinNimGame(tc.heaps)
+		}
+	}
+}

From 214fd2d1e8c4892dcf8b057a217a8a245c0936e1 Mon Sep 17 00:00:00 2001
From: Vasko Zdravevski <vaskoz@users.noreply.github.com>
Date: Wed, 25 Dec 2019 21:44:05 -0700
Subject: [PATCH 2/2] add day 289 to readme

---
 README.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/README.md b/README.md
index fe4c781..c05c33b 100644
--- a/README.md
+++ b/README.md
@@ -300,6 +300,7 @@ problems from
 * [Day 286](https://github.com/vaskoz/dailycodingproblem-go/issues/585)
 * [Day 287](https://github.com/vaskoz/dailycodingproblem-go/issues/587)
 * [Day 288](https://github.com/vaskoz/dailycodingproblem-go/issues/590)
+* [Day 289](https://github.com/vaskoz/dailycodingproblem-go/issues/593)
 * [Day 290](https://github.com/vaskoz/dailycodingproblem-go/issues/594)
 * [Day 291](https://github.com/vaskoz/dailycodingproblem-go/issues/596)
 * [Day 292](https://github.com/vaskoz/dailycodingproblem-go/issues/598)