C++常用的字符串处理函数-全

#include <string.h>
#include <vector>
#include <string>
//字符串分割函数,类似python的split
vector<string> split(char s[],const char *delim)
{
char *token = strtok(s,delim);
vector<string> vstr;
while(token!=NULL){
string stmp = token;
vstr.push_back(stmp);
token = strtok(NULL,delim);
}
return vstr;
}
//若用string调用如下
string s="192.168",sm=".";
vector<string> ss=split(const_cast<char *>(s.c_str()),sm.data());

//参数都为string版
vector<string> split(string s,string delim)
{

char *ss=const_cast<char *>(s.c_str());
const char *ddelim= delim.data();
char *token = strtok(ss,ddelim);
vector<string> vstr;
while(token!=NULL){
string stmp = token;
vstr.push_back(stmp);
token = strtok(NULL,ddelim);
}
return vstr;
}
//以下给出类似于Python 中join功能的实现，后续不断完善
string join(const vector<string> &vs,const string &s)
{
int n=vs.size();
string restr;
for(int i=0;i<n-1;++i)restr=restr+vs[i]+s;
restr +=vs[n-1];
return restr;
}
//char *或vector<char>转string

vector<char> vs;
vs.push_back(char);
vs.push_back('\0'); //特别注意char* 转
string s;
s=string(vs.data());
char a[100]="6666666";
s=string(a);

//列出自己实现的string to int( atoi)
int myAtoi(string str) {
if(str=="")return 0;
if(str.size()==1)
{
if(str[0]>'9'||str[0]<'0')return 0;
}
int beg=0;
while(str[beg]==' ')beg++;//越过前面的空字符
if((str[beg]>'9'||str[beg]<'0')&&str[beg]!='-'&&str[beg]!='+')return 0;//第一个非空字符非法
int sign=(str[beg]=='-')?-1:1; //判断符号
int j=(str[beg]=='+'||str[beg]=='-')?beg+1:beg;//判定何时开始计算
int res=0;
for(int i=j;i<str.size();++i)
{
if(str[i]>'9'||str[i]<'0')break;//遇到非数字即不看后面的内容
res=res*10+(str[i]-'0');
}
return res*sign;
}
//列出自己实现的unsigned int转string，无bug
string itostring(unsigned int a)
{
if(a==0)return "0";
vector<char> vc;
while(a){
unsigned int tmp = a%10;
vc.push_back(tmp+'0');
a=a/10;
}
int n=vc.size();
string s(n,'0');
for(int i=n-1;i>=0;--i)s[n-1-i]=vc[i];
return s;
}
//atoi 或者 itoa  (int to string)int atoi(const char *nptr);
char*itoa(int value,char*string,int radix);
char *strtok(char s[], const char *delim);
//strod字符串转浮点
string = "3.1415926 This stopped it";
x = strtod(string, &stopstring);
printf("string = %s\n", string);
printf("strtod = %f\n", x);
printf("Stopped scan at: %s\n", stopstring);
string = 3.1415926 This stopped it
strtod = 3.141593
Stopped scan at:  This stopped it
string = -1011 This stopped it

1. const char* 和string 转换

(1) const char*转换为 string，直接赋值即可。

EX: const char* tmp = "tsinghua".

string s = tmp;

(2) string转换为const char*，利用c_str()或者data()

EX:  string s = "tsinghua";

const char*tmp = s.c_str();

const char *tmp = s.data();

2. char*和const char*之间的转换

(1) const char*转化为char*，利用const_cast<char*>

EX: const char* tmp = "tsinghua";

char* p = const_cast<char*>(tmp);

(2) char*转化为const char*，直接赋值即可。

char* p = "tsinghua".

const char* tmp = p;

3. char*和string之间的转换

有了1和2的基础，char*和string转化就很简单了。

(1)char*转化为string，直接赋值即可。

EX: char* p = "tsinghua".

string str = p;

(2)string转化为char*，走两步，先是string->const char*，然后是const char*->char*

EX:  string str = "tsinghua";

char* p = const_cast<char*>(str.c_str()):