Merge pull request wangzheng0822#245 from WayneCui/master

add KMP algorithm

go/34_kmp/kmp.go

@@ -0,0 +1,73 @@
+package main
+
+import (
+	"fmt" 
+)
+
+func getNexts(pattern string) []int {
+	m := len(pattern)
+	nexts := make([]int, m)
+	for index := range nexts {
+		nexts[index] = -1
+	}
+
+	for i := 1; i < m - 1; i++ {
+		j := nexts[i - 1]
+
+		for pattern[j + 1] != pattern[i] && j >= 0 {
+			j = nexts[j]
+		}
+
+		if pattern[j + 1] == pattern[i] {
+			j += 1
+		}
+
+		nexts[i] = j
+	}
+
+	return nexts
+}
+
+func findByKMP(s string, pattern string) int {
+	n := len(s)
+	m := len(pattern)
+	if n < m {
+		return -1
+	}
+
+	nexts := getNexts(pattern)
+
+	j := 0
+	for i := 0; i < n; i++ {
+		for j > 0 && s[i] != pattern[j] {
+			j = nexts[j - 1] + 1
+		}
+
+		if s[i] == pattern[j] {
+			if j == m - 1 {
+				return i - m + 1
+			}
+			j += 1
+		}
+	}
+
+	return -1
+}
+
+func main(){
+	s := "abc abcdab abcdabcdabde"
+	pattern := "bcdabd"
+	fmt.Println(findByKMP(s, pattern)) //16
+
+	s = "aabbbbaaabbababbabbbabaaabb"
+	pattern = "abab"
+	fmt.Println(findByKMP(s, pattern)) //11
+
+	s = "aabbbbaaabbababbabbbabaaabb"
+	pattern = "ababacd"
+	fmt.Println(findByKMP(s, pattern)) //-1
+
+	s = "hello"
+	pattern = "ll"
+	fmt.Println(findByKMP(s, pattern)) //2
+}