shared prefix go

sharedprefix.go

package sharedprefix

func SharedPrefix(vs []string) string {
	if len(vs) == 0 {
		return ""
	}

	l := len(vs[0])
	for _, s := range vs[1:] {
		if l > len(s) {
			l = len(s)
		}
	}

	for i := 0; i < l; i++ {
		for _, s := range vs[1:] {
			if vs[0][i] != s[i] {
				return vs[0][0:i]
			}
		}
	}

	return vs[0][0:l]
}

sharedprefix_test.go

package sharedprefix_test

func TestSharedPrefix(t *testing.T) {
	testCases := []struct {
		vs     []string
		shared string
	}{
		{vs: []string{}, shared: ""},
		{vs: []string{""}, shared: ""},
		{vs: []string{"a"}, shared: "a"},
		{vs: []string{"a", "a"}, shared: "a"},
		{vs: []string{"aa", "ab"}, shared: "a"},
		{vs: []string{"aa", "aa"}, shared: "aa"},
		{vs: []string{"abc", "abc", "ab"}, shared: "ab"},
		{vs: []string{"ab", "abc", "ab"}, shared: "ab"},
		{vs: []string{"abc", "abc", "abd"}, shared: "ab"},
	}
	for _, tC := range testCases {
		t.Run(fmt.Sprintf("%v", tC.vs), func(t *testing.T) {
			actual := query.SharedPrefix(tC.vs)
			if tC.shared != actual {
				t.Errorf("expected %v, got %v", tC.shared, actual)
			}
		})
	}
}