add kmp

Author: shellfly

README.md

@@ -77,6 +77,7 @@ To test each algorithm(data structure), instead of running the file directly, yo
   * [Quick3string](algs4/quick3_string.go)
   * [TrieST](algs4/trie_st.go)
   * [TST](algs4/tst.go)
+  * [KMP](algs4/kmp.go)
 
 
 ## License

algs4/kmp.go

@@ -0,0 +1,49 @@
+package algs4
+
+// KMP ...
+type KMP struct {
+	pattern string
+	dfa     [][]int
+}
+
+// makeTwoD return a two dimensional slice
+func makeTwoD(rows, columns int) [][]int {
+	twoD := make([][]int, rows)
+	for i := 0; i < rows; i++ {
+		twoD[i] = make([]int, columns)
+	}
+	return twoD
+}
+
+// NewKMP ...
+func NewKMP(pattern string) *KMP {
+	R := 256
+	M := len(pattern)
+	dfa := makeTwoD(R, M)
+	k := &KMP{pattern, dfa}
+	dfa[pattern[0]][0] = 1
+	X := 0
+	for j := 1; j < M; j++ {
+		for c := 0; c < R; c++ {
+			dfa[c][j] = dfa[c][X]
+		}
+		dfa[pattern[j]][j] = j + 1
+		X = dfa[pattern[j]][X]
+	}
+	return k
+}
+
+// Search ...
+func (k *KMP) Search(txt string) int {
+	N, M := len(txt), len(k.pattern)
+	var i, j int
+	for i, j = 0, 0; i < N && j < M; i++ {
+		j = k.dfa[txt[i]][j]
+	}
+	// Found (hit end of pattern)
+	if j == M {
+		return i - M
+	}
+	// Not Found (hit end of text)
+	return N
+}

cmd/kmp/main.go

@@ -0,0 +1,50 @@
+/******************************************************************************
+ *  Execution:    go run cmd/kmp/main.go pattern text
+ *
+ *  Reads in two strings, the pattern and the input text, and
+ *  searches for the pattern in the input text using the
+ *  KMP algorithm.
+ *
+ *  % go run cmd/kmp/main.go abracadabra abacadabrabracabracadabrabrabracad
+ *  text:    abacadabrabracabracadabrabrabracad
+ *  pattern:               abracadabra
+ *
+ *  % go run cmd/kmp/main.go rab abacadabrabracabracadabrabrabracad
+ *  text:    abacadabrabracabracadabrabrabracad
+ *  pattern:         rab
+ *
+ *  % go run cmd/kmp/main.go bcara abacadabrabracabracadabrabrabracad
+ *  text:    abacadabrabracabracadabrabrabracad
+ *  pattern:                                   bcara
+ *
+ *  % go run cmd/kmp/main.go rabrabracad abacadabrabracabracadabrabrabracad
+ *  text:    abacadabrabracabracadabrabrabracad
+ *  pattern:                        rabrabracad
+ *
+ *  % go run cmd/kmp/main.go abacad abacadabrabracabracadabrabrabracad
+ *  text:    abacadabrabracabracadabrabrabracad
+ *  pattern: abacad
+ *
+ ******************************************************************************/
+
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/shellfly/algo/algs4"
+)
+
+func main() {
+	pat, txt := os.Args[1], os.Args[2]
+	kmp := algs4.NewKMP(pat)
+	offset := kmp.Search(txt)
+	fmt.Println("offset: ", offset)
+	fmt.Println("text:    " + txt)
+	fmt.Print("pattern: ")
+	for i := 0; i < offset; i++ {
+		fmt.Print(" ")
+	}
+	fmt.Println(pat)
+}