BM(Boyer-Moore)字符串匹配算法的实现(一种有效常用的字符串匹配算法)

]/*******************************************************************
*
*    DESCRIPTION:Boyer-Moore Algorithm for String (BM Algorithm)
*
*    AUTHOR:NeeSky
*
*    DATE:2009-9-10
*
*******************************************************************/
/** include files **/
#include <iostream>
using namespace std;
/**
*
* Compare Two string from Tail, and return the max commo  chars
*
* @author NeeSky (2009-9-14)
*
* @param strSample :Given Sample string
* @param tail : tail position of strSample
* @param strTemplate :Given template string
*
* @return int : the max common chars length
*/
int CommonChars_fromTailStart(const string& strSample,int tail,const string strTemplate )
{
assert(tail<strSample.length()&&strSample.length()>=strTemplate.length());/*Proper Parameters List*/
int i;/*How many chars matched from tail*/
for(i=0;i<strTemplate.length();++i)
{
if(strSample[tail-i]!=strTemplate[strTemplate.length()-i-1])
break;
}
return i;
}
/**
* BM String Match Core Algorithm[Letter Case Sense]
*
* @author NeeSky (2009-9-13)
*
* @param strSample:    Sample String
* @param strTemplate:  Template String
*
* @return int : first char position of string matched(start 0)
*/
int BM_StringMatch(const string& strSample,const string& strTemplate)
{
if(strTemplate==""||(strTemplate.length()>strSample.length()))return -1;/*Not Exist in strSample*/
int lenTemplate=strTemplate.length(),lenSample=strSample.length();
int tail=lenTemplate-1;/*init the start and tail position*/
while(tail<lenSample)
{
int numSameChars=CommonChars_fromTailStart(strSample,tail,strTemplate);
if(numSameChars==lenTemplate)
return tail-lenTemplate+1;/*The First Match Position*/
if(numSameChars==0)
++numSameChars;/*Just Jump One Position*/
tail+=numSameChars;/*Jump numSameChars Position*/
}
return -1;/*Not Match in Sample String*/
}
/**
* Output the Problem info. ,just call BM_StringMatch function
*
* @author NeeSky (2009-9-14)
*
* @param strSample: Sample String
* @param strTemplate: Sample String
*/
void SolveProblemOutput(const string strSample,const string strTemplate)
{
cout<<"Sample String:   "<<strSample<<";    Template String:"<<strTemplate<<";"<<endl;
int pos=BM_StringMatch(strSample,strTemplate);
if(pos==-1)
cout<<"Sorry,No Match!"<<endl<<endl;
else
cout<<"Match Pos: "<<pos<<endl<<endl;
return;
}

/**
* For Boyer-Moore String Algorithm, A effective algorithm
*
* @author NeeSky (2009-9-10)
*
* @return int
*/
int main(void)
{
/*Testing Cases*/
SolveProblemOutput("a simple example","example");
SolveProblemOutput("My Happiness is your happiness","happiness");
SolveProblemOutput("My Happinessis is your happiness"," is");
return 0;
}