利用已知的进行分割字符串的算法

#include <vector>
#include <string>
#include <iostream>
#include <algorithm>
using namespace std;


typedef basic_string<char>::size_type S_T;  
static const S_T npos = -1;  


////trim指示是否保留空串，默认为保留。tok可以为任意多个字符
vector<string> tokenize(const string& src, string tok,            
bool trim=false, string null_subst="")  
{  
if( src.empty() || tok.empty() ) 
throw "tokenize: empty string\0";  


vector<string> v;  
S_T pre_index = 0, index = 0, len = 0;  
while( (index = src.find_first_of(tok, pre_index)) !=npos )  
{  
if( (len = index-pre_index)!=0 )  
v.push_back(src.substr(pre_index, len));  
else if(trim==false)  
v.push_back(null_subst);  
pre_index = index+1;  
}  
string endstr = src.substr(pre_index);  
if( trim==false ) v.push_back( endstr.empty()?null_subst:endstr );  
else if( !endstr.empty() ) 
v.push_back(endstr);  
return v;  

} 

//delimit为一个字符，严格分割
vector<string> split(const string& src, string delimit, string null_subst="")  
{  
if( src.empty() || delimit.empty() ) 
throw "split:empty string\0";    
vector<string> v;  
S_T deli_len = delimit.size();  
long index = npos, last_search_position = 0;  
while( (index=src.find(delimit,     
last_search_position))!=npos )  
{  
if(index==last_search_position)  
v.push_back(null_subst);  
else  
v.push_back( src.substr(last_search_position, index-   
last_search_position) );  
last_search_position = index + deli_len;  
}  
string last_one = src.substr(last_search_position);  
v.push_back( last_one.empty()? null_subst:last_one );  
return v;  
}   


//测试如下：
int main(int argc, char* argv[])
{
string src = ",ab,cde;,,fg,," ;  
string tok = "," ;   
vector<string> v1 = tokenize(src, tok ,true);  
vector<string> v2 = tokenize(src, tok ,false,     
"<null>");    
cout<<"-------------v1:"<<endl;  
for(int i=0; i<v1.size();i++)  
{  
cout<<v1[i].c_str()<<endl;  
}   
cout<<"-------------v2:"<<endl;  
for(int j=0; j<v2.size();j++)  
{  
cout<<v2[j].c_str()<<endl;  
}  
try{  


string s = "1;2;3;4";  
string del = ";";//"###";  
vector<string> v3 = split(s, del, "<null>");  
cout<<"-------------v3:"<<endl;  
for(int k=0; k<v3.size();k++)  
{  
cout<<v3[k].c_str()<<endl;  
}  
}  
catch (char *s) {  
cout<<s<<endl;  
}
return 0;
}