【模板】字符串处理 （STL使用）

有关的字符串问题的基础使用 

#include<bits/stdc++.h>
using namespace std;
int main(void)
{
	string str1="March";
	string str2="11th";
	//原型 const char *c_str() 
	//注意 c_str()返回一个指向正规C字符串的指针，内容和string类对象相同 
	const char *first=str1.c_str();
	const char *second=str2.c_str();
	char *merge=new char[strlen(first)+strlen(second)+1];//动态申请内存空间 
	strcpy(merge,first);
	strcat(merge,second);
	
	printf("%s\n",merge);//C输出字符串 
	cout<<merge<<endl;//C++直接输出merge指向的字符串(C++为了方便专门设计)
	cout<<*merge<<endl;//输出第一个字符M
	
	//和整型数组对比 
	int a[2]={5,1};
	cout<<a<<endl;//输出a的指针 
	cout<<*a<<endl; //输出第一个元素5 
	
	delete []merge;
	return 0;
}

 

 //STL string基本字符串(第一部分)
 //和C/C++比较
#include<cstring>
#include<iostream>
using namespace std;
int main(void)
{
	string s;
	s="March 12th";
	cout<<"Length:"<<s.length()<<"\t"<<"Text:"<<s<<endl;
	
	/*直接把字符串赋值给string*/
	char ss[15]="March 13th";
	s=ss;//直接赋值 
	cout<<"Length:"<<s.length()<<"\t"<<"Text:"<<s<<endl;
	 
	 /*把string类赋值给数组*/
	 char ss2[15];
	 string s2="2019 03 12";
	 strcpy(ss2,s2.c_str());
	 cout<<"Length:"<<s2.length()<<"\t"<<"Text:"<<ss2<<endl;
	 //cout可以直接输出char字符串和string,也可以用printf
	 
	 /*尾部追加字符串(+/append())*/
	 s2=s2+" Z";
	 s2.append(" X");
	 cout<<"Append:"<<s2<<endl; 
	 
	 /*插入字符*/
	 string name="University"; 
	 string::iterator it;
	 it=name.begin();
	 name.insert(it+3,'h');//插入字符用单引号 
	 cout<<"Insert:"<<name<<"\t"<<"1st:"<<name[0]<<endl;
	 
	 /*删除元素*/
	 name.erase(it);//删除单个元素 
	 cout<<"1st Delete:"<<name<<"\t";
	 name.erase(name.begin(),name.begin()+7);//元素位置从0开始计数 
	 cout<<"2nd Delete:"<<name<<endl;
	 
	return 0;
} 
  

//STL string基本字符串(第二部分)
#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
int main(void)
{
	/*替换string对象的字符*/
	string s="123456789";
	s.replace(3,3,"cs cs");//从下标为3的字符开始,将连续的3个字符，替换为"cs" 
	cout<<"Replace:"<<s<<endl;
	
	/*搜索string的元素或者子串*/
	s="apple pear";
	cout<<"Index for a:"<<s.find('a')<<"\t";//输出第一个下标
	cout<<"Index for pp:"<<s.find("pp")<<endl;
	
	/*字符串比较*/
	s="cat dog cat";
	string ss="cat";
	string sss="Cat";
	cout<<"s compare with ss:"<<s.compare(ss)<<"\t"; 
	cout<<"ss compare with sss:"<<s.compare("Cat")<<endl;
	//大写A 65 41H 小写97 61H  
	
	/*字符串翻转*/
	reverse(sss.begin(),sss.end());//属于algorithm 
	cout<<"Reverse:"<<sss<<endl; 
	
	/*利用string进行数位处理*/
	string num="314159";
	int sum=0;
	for(int i=0;i<num.length();i++)
	{
		sum+=num[i]-'0';
	 } 
	 cout<<"The sum of num:"<<sum<<endl;
	
	/*string和字符数组相互操作*/
	string str1;
	char str2[20]="abcabc";
	str1=str2;
	cout<<"字符数组可以直接赋值string："<<str2<<endl;
	
	str1.append("def");
	cout<<"string要经过c_str()才能转换："<<str1.c_str()<<endl;
	strcpy(str2,str1.c_str());
	cout<<"采用strcpy把string存储到字符数组：" <<str2<<endl;
	 
	 return 0;
 } 

 

//STL
//
#include<iostream>
#include<cstring>
#include<algorithm>
#include<sstream> 
using namespace std;
int main(void)
{
	/*sscanf 将字符串按照一定格式分离字符串*/
	//牛客:日志排序 
	char s[101];int n=4;
	while(n--)
	{
		int year ;int month;int day;
		scanf("%s",&s);
		sscanf(s,"%4d%2d%2d",&year,&month,&day);
		printf("%d %d %d\n",year,month,day); 
	}
	
	return 0;
 } 
 

//STL
#include<iostream>
#include<cstring>
#include<algorithm>
#include<sstream> 
using namespace std;
string doubleToString(double x)
{
	ostringstream os;//定义输出流 
	if(os<<x) return os.str();
 } 
 double stringToDouble(const string &s)
 {
 	istringstream i(s);
 	double x;
 	if(i>>x) return x;
 }
int main(void)
{
	/*string和数值相互转换*/
	/*数值转换成string C方法*/
	char b[10];
	string a;
	sprintf(b,"%d",1922);//把数据格式化输出到某个字符串 
	cout<<"数值转换string(sprintf):"<<b<<endl;
	
	/*数值转换为string C++ */ 
	string cc=doubleToString(1998.1022);
	cout<<"数值转换string(ostringstream):"<< cc<<endl; 
	
	/*string转换成数值 C++*/
	string dd="2020";
	int p= stringToDouble(dd);
	cout<<"string转换数值(istringstream):" <<p<<endl;
	return 0;
 }