Merge 76c9e07 into f6d47f1

README.md

@@ -273,3 +273,4 @@ problems from
 * [Day 260](https://github.com/vaskoz/dailycodingproblem-go/issues/533)
 * [Day 266](https://github.com/vaskoz/dailycodingproblem-go/issues/542)
 * [Day 268](https://github.com/vaskoz/dailycodingproblem-go/issues/544)
+* [Day 269](https://github.com/vaskoz/dailycodingproblem-go/issues/547)

day269/problem.go

@@ -0,0 +1,33 @@
+package day269
+
+// SimulateDominoes runs a simulation of dominoes falling
+// based on an initial state. It returns the end state.
+func SimulateDominoes(initial string) string {
+	start := make([]rune, len([]rune(initial)))
+	copy(start, []rune(initial))
+	result := make([]rune, len(start))
+	changed := true
+	for changed {
+		changed = false
+		for i, domino := range start {
+			if domino == '.' {
+				switch {
+				case i != 0 && i != len(start)-1 && start[i-1] == 'R' && start[i+1] == 'L':
+					result[i] = start[i]
+				case i != 0 && start[i-1] == 'R':
+					result[i] = 'R'
+					changed = true
+				case i != len(start)-1 && start[i+1] == 'L':
+					result[i] = 'L'
+					changed = true
+				default:
+					result[i] = start[i]
+				}
+			} else {
+				result[i] = start[i]
+			}
+		}
+		copy(start, result)
+	}
+	return string(result)
+}

day269/problem_test.go

@@ -0,0 +1,28 @@
+package day269
+
+import "testing"
+
+// nolint
+var testcases = []struct {
+	start, end string
+}{
+	{".L.R....L", "LL.RRRLLL"},
+	{"..R...L.L", "..RR.LLLL"},
+}
+
+func TestSimulateDominoes(t *testing.T) {
+	t.Parallel()
+	for _, tc := range testcases {
+		if result := SimulateDominoes(tc.start); result != tc.end {
+			t.Errorf("Given %s, expected %s, got %s", tc.start, tc.end, result)
+		}
+	}
+}
+
+func BenchmarkSimulateDominoes(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			SimulateDominoes(tc.start)
+		}
+	}
+}