Merge pull request #350 from vaskoz/day167

Day167

README.md

@@ -178,3 +178,4 @@ problems from
 * [Day 164](https://github.com/vaskoz/dailycodingproblem-go/issues/340)
 * [Day 165](https://github.com/vaskoz/dailycodingproblem-go/issues/343)
 * [Day 166](https://github.com/vaskoz/dailycodingproblem-go/issues/346)
+* [Day 167](https://github.com/vaskoz/dailycodingproblem-go/issues/347)

day167/problem.go

@@ -0,0 +1,34 @@
+package day167
+
+// Pair represents indicies that correspond to words
+// that when concatenated result in a palindrome.
+type Pair struct {
+	First, Second int
+}
+
+// PairsPalindromes returns a slice of Pairs.
+// Runs in O(N^2) time.
+func PairsPalindromes(words []string) []Pair {
+	var result []Pair
+	for i, first := range words {
+		for j, second := range words {
+			if i == j {
+				continue
+			}
+			combined := first + second
+			if isPalindrome(combined) {
+				result = append(result, Pair{i, j})
+			}
+		}
+	}
+	return result
+}
+
+func isPalindrome(s string) bool {
+	for i := 0; i < len(s)/2; i++ {
+		if s[i] != s[len(s)-1-i] {
+			return false
+		}
+	}
+	return true
+}

day167/problem_test.go

@@ -0,0 +1,30 @@
+package day167
+
+import (
+	"reflect"
+	"testing"
+)
+
+var testcases = []struct {
+	words    []string
+	expected []Pair
+}{
+	{[]string{"code", "edoc", "da", "d"}, []Pair{{0, 1}, {1, 0}, {2, 3}}},
+}
+
+func TestPairsPalindromes(t *testing.T) {
+	t.Parallel()
+	for _, tc := range testcases {
+		if result := PairsPalindromes(tc.words); !reflect.DeepEqual(tc.expected, result) {
+			t.Errorf("Expected %v got %v", tc.expected, result)
+		}
+	}
+}
+
+func BenchmarkPairsPalindromes(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			PairsPalindromes(tc.words)
+		}
+	}
+}