Add Rabin-Karp Algorithm

Author: ua-nick

.travis.yml

@@ -18,4 +18,5 @@ script:
   cd ../MergeSort && go test ./;
   cd ../SelectionSort && go test ./;
   cd ../TernarySearch && go test ./;
-  cd ../NaiveStringSearch && go test ./;
+  cd ../NaiveStringSearch && go test ./;
+  cd ../RabinKarp && go test ./;

README.md

@@ -29,6 +29,7 @@ There are several data structures and algorithms implemented in this project. Th
 ##### String searching algorithms
 
 - Naive String Search
+- Rabin-Karp Algorithm
 
 ##### Sorting algorithms
 - Selection Sort

RabinKarp/RabinKarp.go

@@ -0,0 +1,31 @@
+package RabinKarp
+
+import "hash/adler32"
+
+func calculateHash(text string) uint32 {
+	return adler32.Checksum([]byte(text))
+}
+
+func RabinKarp(text, pattern string) int {
+	textLength := len(text)
+	patternLength := len(pattern)
+	if patternLength > textLength {
+		return -1
+	}
+	for i := 0; i < textLength-patternLength+1; i++ {
+		if calculateHash(pattern) != calculateHash(text[i:i+patternLength]) {
+			continue
+		}
+		matchesCount := 0
+		for j := 0; j < patternLength; j++ {
+			if text[i+j] != pattern[j] {
+				break
+			}
+			matchesCount++
+		}
+		if matchesCount == patternLength {
+			return i
+		}
+	}
+	return -1
+}

RabinKarp/RabinKarp_test.go

@@ -0,0 +1,22 @@
+package RabinKarp
+
+import (
+	"math/rand"
+	"testing"
+	"time"
+)
+
+func TestRabinKarp(t *testing.T) {
+	random := rand.New(rand.NewSource(time.Now().UnixNano()))
+	letters := []rune("abcdefghijklmnopqrstuvwxyz")
+	text := make([]rune, random.Intn(15-10)+10)
+	for i := range text {
+		text[i] = letters[rand.Intn(len(letters))]
+	}
+	end := random.Intn(len(text)-5) + 5
+	start := random.Intn(end)
+	result := RabinKarp(string(text), string(text[start:end]))
+	if result == -1 {
+		t.Fail()
+	}
+}