string中常用的函数

发现在string在处理这符串是很好用,就找了一篇文章放在这里了..

用 string来代替char * 数组，使用sort排序算法来排序，用unique 函数来去重
1、Define
           string s1 = "hello";
           string s2 = "world";
           string s3 = s1 + "," + s2 +"!\n";
2、append
           s1 += ",shanshan\n";
3、Compare
           if(s1 == s2)
              .....
           else if(s1 == "hello")
              .....
4、 string 重载了许多操作符，包括 +, +=, <, =, , [], <<, >>等，正式这些操作符，对字符串操作非常方便

#include <string>
#include <iostream>
using namespace std;
int main(){
           string strinfo="Please input your name:";
           cout << strinfo ;
           cin >> strinfo;
        if( strinfo == "winter" )
           cout << "you are winter!"<<endl;
        else if( strinfo != "wende" )
           cout << "you are not wende!"<<endl;
        else if( strinfo < "winter")
           cout << "your name should be ahead of winter"<<endl;
        else 
           cout << "your name should be after of winter"<<endl;
           strinfo += " , Welcome to China!";
           cout << strinfo<<endl;
           cout <<"Your name is :"<<endl;
           string strtmp = "How are you? " + strinfo;
        for(int i = 0 ; i < strtmp.size(); i ++)
           cout<<strtmp[i];
        return 0;
} 

size_type find_first_of(const basic_string& s, size_type pos = 0)
size_type find_first_of(const charT* s, size_type pos, size_type n)
size_type find_first_of(const charT* s, size_type pos = 0)
size_type find_first_of(charT c, size_type pos = 0)

所有的查找函数都返回一个size_type类型，这个返回值一般都是所找到字符串的位置，如果没有找到，则返回string::npos。
其实string::npos表示的是-1。即没找到就返回-1。例子如下：
#include <string>
#include <iostream>
using namespace std;
int main(){
           string strinfo="      //*---Hello Word!......------";
           string strset="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
        int first = strinfo.find_first_of(strset);
        if(first == string::npos) { 
                   cout<<"not find any characters"<<endl;
                return -1;
           } 
        int last = strinfo.find_last_of(strset);
        if(last == string::npos) { 
                   cout<<"not find any characters"<<endl;
                return -1;
           } 
           cout << strinfo.substr(first, last - first + 1)<<endl;//string.substr是子串
        return 0;
}
6、insert函数, replace函数和erase函数

string只是提供了按照位置和区间的replace函数，而不能用一个string字串来替换指定string中的另一个字串。
例子：
#include <string>
#include <iostream>
using namespace std;
int main() {
           string strinfo="This is Winter, Winter is a programmer. Do you know Winter?";
           cout<<"Orign string is :\n"<<strinfo<<endl;
           string_replace(strinfo, "Winter", "wende");
           cout<<"After replace Winter with wende, the string is :\n"<<strinfo<<endl;
        return 0;
}

string.erase(pos,srclen);//srclen是删除的长度
string.insert(pos,strdst); //pos是定位，strdst是插入的函数
void string_replace(string & strBig, const string & strsrc, const string &strdst) {
           string::size_type pos=0;
           string::size_type srclen=strsrc.size();
           string::size_type dstlen=strdst.size();
        while( (pos=strBig.find(strsrc, pos)) != string::npos){
                   strBig.erase(pos, srclen);
                   strBig.insert(pos, strdst);
                   pos += dstlen;
           }
}