substr 的用法

#include<string>
#include<vector>
#include<map>

#include<iostream>
using namespace std;

int main(void)
{
vector<string> vec;
vector<string>::iterator it;
int beg = 0;
int end;
string str = "dog cat cat dog boy";

while(true)
{
end = str.find(" ",beg);
vec.push_back(str.substr(beg,end-beg));

if(end == string::npos)
{
break;
}
beg = end + 1;
}

for(it = vec.begin(); it != vec.end(); it++)
{
cout<<*it<<end;                //cout:     dog        cat      cat    dog     boy
}
reuturn 0;
}

切记：substr的第二个参数是表示从第一个参数的位置开始后的多少个字符