Java implementation of Boyer-moore algorithm

Boyer-moore Understanding Reference Blog

This article records the Java implementation of the Boyer-moore algorithm.

Import java.util.*;p Ublic class Boyermoore {public static void main (string[] args) {String text= "China is a great country; great Motherland"; String pattern= "The Great Kingdom"; Boyermoore bm=new Boyermoore (); Bm.boyermoore (pattern, text);} private void PREBMBC (String pattern,int patlength,map<string,integer> bmbc) {System.out.println ("BMBC start Process ... "); for (int i=patlength-2;i>=0;i--) {if (!bmbc.containskey (string.valueof (Pattern.charat (i))) { Bmbc.put (string.valueof (Pattern.charat (i)), (Integer) (patlength-i-1));}}} private void suffix (String pattern,int patlength,int [] suffix) {suffix[patlength-1]=patlength;int q=0;for (int i= patlength-2;i>=0;i--) {q=i;while (Q>=0&&pattern.charat (q) ==pattern.charat (patLength-1-i+q)) {q--;} Suffix[i]=i-q;}} private void Prebmgs (String pattern,int patlength,int []bmgs) {int I,j;int []suffix=new int[patlength];suffix (Pattern, Patlength,suffix);//The string does not match a good suffix, and a maximum prefix for (i=0;i<patlength;i++) {bmgs[i]=patlength is not found;} No substring in the pattern string matches the good suffix, but finds a maximum prefix j=0;for (i=patlength-1;i>=0;i--) {if (suffix[i]==i+1) {for (; j<patlength-1-i;j++) {if (bmgs[j]==patlength) {bmgs[j]=patlength-1-i;}}}} There are substrings in the pattern string that match the suffix for (i=0;i<patlength-1;i++) {bmgs[patlength-1-suffix[i]]=patlength-1-i;} System.out.print ("Bmgs:"); for (i=0;i<patlength;i++) {System.out.print (bmgs[i]+ ",");} System.out.println ();} private int GETBMBC (String c,map<string,integer> bmbc,int m) {//returns the length of the pattern if the corresponding value is returned in the rule if ( Bmbc.containskey (c)) {return bmbc.get (c);} Else{return m;}} public void Boyermoore (String pattern,string text) {int m=pattern.length (); int n=text.length (); Map<string,integer> bmbc=new hashmap<string,integer> (); int[] Bmgs=new INT[M];//PROPROCESSINGPREBMBC ( PATTERN,M,BMBC);p Rebmgs (pattern,m,bmgs)//searchingint j=0;int i=0;int count=0;while (j<=n-m) {for (i=m-1;i>=0 &&pattern.charat (i) ==text.charat (i+j); i--) {//For counting count++;} if (i<0) {System.out.println ("one position is:" +j); j+=bmgs[0];} Else{j+=math.max (BMGS[I],GETBMBC (string.valueof (Text.charat (i+j), bmbc,m)-m+1+i);}} System.out.println ("Count:" +count);}} 

Java implementation of Boyer-moore algorithm