add problem 10 - Regular Expression Matching

Author: anirudhology

problems/dynamic_programming/regular_expression_matching.go

@@ -0,0 +1,37 @@
+package dynamic_programming
+
+func RegularExpressionMatching(s string, p string) bool {
+	// Length of strings
+	m, n := len(s), len(p)
+	// Lookup table to store if s[0...i] matches p[0...j]
+	lookup := make([][]bool, m+1)
+	for i := range lookup {
+		lookup[i] = make([]bool, n+1)
+		for j := range lookup[i] {
+			lookup[i][j] = false
+		}
+	}
+	// Empty string matches with empty patten
+	lookup[0][0] = true
+	// For empty string and star pattern
+	for j := 2; j <= n; j++ {
+		if p[j-1] == '*' {
+			lookup[0][j] = lookup[0][j-2]
+		}
+	}
+	// Populate remaining table
+	for i := 1; i <= m; i++ {
+		for j := 1; j <= n; j++ {
+			// If characters are same or pattern is period
+			if s[i-1] == p[j-1] || p[j-1] == '.' {
+				lookup[i][j] = lookup[i-1][j-1]
+			} else if j > 1 && p[j-1] == '*' {
+				lookup[i][j] = lookup[i][j-2]
+				if p[j-2] == '.' || p[j-2] == s[i-1] {
+					lookup[i][j] = lookup[i][j] || lookup[i-1][j]
+				}
+			}
+		}
+	}
+	return lookup[m][n]
+}

tests/dynamic_programming/regular_expression_matching_test.go

@@ -0,0 +1,31 @@
+package dynamic_programming_test
+
+import (
+	"testing"
+
+	"github.com/anirudhology/leetcode-go/problems/dynamic_programming"
+)
+
+func TestIsMatch(t *testing.T) {
+	tests := []struct {
+		s, p   string
+		result bool
+	}{
+		{"aa", "a*", true},
+		{"ab", ".*", true},
+		{"mississippi", "mis*is*p*.", false},
+		{"aab", "c*a*b", true},
+		{"ab", "a", false},
+		{"", ".*", true},
+		{"", "a*", true},
+		{"abcd", "d*", false},
+		{"aaa", "a*a", true},
+		{"aaa", "ab*a", false},
+	}
+
+	for _, test := range tests {
+		if got := dynamic_programming.RegularExpressionMatching(test.s, test.p); got != test.result {
+			t.Errorf("isMatch(%v, %v) = %v; want %v", test.s, test.p, got, test.result)
+		}
+	}
+}