regex!

regx/readme.md

@@ -0,0 +1,41 @@
+10. Regular Expression Matching
+Hard
+
+Given an input string s and a pattern p, implement regular expression matching with support for '.' and '*' where:
+
+    '.' Matches any single character.​​​​
+    '*' Matches zero or more of the preceding element.
+
+The matching should cover the entire input string (not partial).
+
+ 
+
+Example 1:
+
+Input: s = "aa", p = "a"
+Output: false
+Explanation: "a" does not match the entire string "aa".
+
+Example 2:
+
+Input: s = "aa", p = "a*"
+Output: true
+Explanation: '*' means zero or more of the preceding element, 'a'. Therefore, by repeating 'a' once, it becomes "aa".
+
+Example 3:
+
+Input: s = "ab", p = ".*"
+Output: true
+Explanation: ".*" means "zero or more (*) of any character (.)".
+
+ 
+
+Constraints:
+
+    1 <= s.length <= 20
+    1 <= p.length <= 30
+    s contains only lowercase English letters.
+    p contains only lowercase English letters, '.', and '*'.
+    It is guaranteed for each appearance of the character '*', there will be a previous valid character to match.
+
+

regx/regx.go

@@ -0,0 +1,35 @@
+package regx
+
+func isCharMatch(text, pattern string) bool {
+	return pattern[0] == '.' || pattern[0] == text[0]
+}
+
+func matchStar(text, pattern string) bool {
+	for {
+		switch {
+		case isMatch(text, pattern[2:]):
+			return true
+		case text == "" || !isCharMatch(text, pattern):
+			return false
+		default:
+			text = text[1:]
+		}
+	}
+}
+
+func isMatch(text, pattern string) bool {
+	switch {
+	case pattern == "":
+		return text == ""
+	case len(pattern) >= 2 && pattern[1] == '*':
+		return matchStar(text, pattern)
+	case text != "" && isCharMatch(text, pattern):
+		return isMatch(text[1:], pattern[1:])
+	}
+
+	return false
+}
+
+func IsMatch(text, pattern string) bool {
+	return isMatch(text, pattern)
+}

regx/regx_test.go

@@ -0,0 +1,52 @@
+package regx_test
+
+import (
+	"testing"
+
+	"git.jxs.me/leetgo/regx"
+	"github.com/stretchr/testify/require"
+)
+
+func TestEmpty(t *testing.T) {
+	require.True(t, regx.IsMatch("", ""))
+}
+
+func TestSingleMatch(t *testing.T) {
+	require.True(t, regx.IsMatch("a", "a"))
+}
+
+func TestSingleNonMatch(t *testing.T) {
+	require.False(t, regx.IsMatch("b", "a"))
+}
+
+func TestMultiMatch(t *testing.T) {
+	require.True(t, regx.IsMatch("aba", "aba"))
+}
+
+func TestMultiNonMatch(t *testing.T) {
+	require.False(t, regx.IsMatch("abca", "abac"))
+}
+
+func TestWildMatch(t *testing.T) {
+	require.True(t, regx.IsMatch("hello", "h.ll."))
+}
+
+func TestWildNonMatch(t *testing.T) {
+	require.False(t, regx.IsMatch("hello", "hall."))
+}
+
+func TestManyMatch(t *testing.T) {
+	require.True(t, regx.IsMatch("greeet", "gre*t"))
+}
+
+func TestManyMisMatch(t *testing.T) {
+	require.True(t, regx.IsMatch("greet", "gre*a*t"))
+}
+
+func TestWildcardManyMatch(t *testing.T) {
+	require.True(t, regx.IsMatch("anything", ".*"))
+}
+
+func TestWildcardNonGreedyMatch(t *testing.T) {
+	require.True(t, regx.IsMatch("bbba", ".*a"))
+}