C++学习之字符串转数字,数字转字符串

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1. 字符串转数字

　　如将“32”转为32，将“3.1415”转为3.1415，将“567283”转为567283。使用：

//Convert string to integer, more @http://www.cplusplus.com/reference/clibrary/cstdlib/atoi/int atoi ( const char * str );//Convert string to double, more @http://www.cplusplus.com/reference/clibrary/cstdlib/atof/double atof ( const char * str ); // Convert string to long integer,more @http://www.cplusplus.com/reference/clibrary/cstdlib/atol/long int atol ( const char * str );  //Read formatted data from string, more @http://www.cplusplus.com/reference/clibrary/cstdio/sscanf/int sscanf ( const char * str, const char * format, ...);

例子1：

Example1/* atoi,atof,atol example */#include <stdio.h>#include <stdlib.h>int main (){  int a;float b;long c;  a=atoi("32");  b=atof("3.1415");  c=atol("567283");  printf ("%d,%f,%d",a,b,c);   return 0;}Output:32,3.141500,567283

例子2：

Example2/* sscanf example */#include <stdio.h>int main (){  int a;float b;long c;  sscanf ("32,3.1415,567283","%d,%f,%d",&a,&b,&c);  printf ("%d,%f,%d",a,b,c);     return 0;}Output:32,3.141500,567283

2. 数字转字符串

如将32转为“32”，将3.1415转为“3.1415”，将567283转为“567283”。使用：

//Write formatted data to string, more @http://www.cplusplus.com/reference/clibrary/cstdio/sprintf/int sprintf ( char * str, const char * format, ... );//Convert integer to string (non-standard function), more @http://www.cplusplus.com/reference/clibrary/cstdlib/itoa///This function is not defined in ANSI-C and is not part of C++, but is supported by some compilers.//A standard-compliant alternative for some cases may be sprintf.char *  itoa ( int value, char * str, int base );

例子3：

Example3/* sprintf example */#include <stdio.h>int main (){  char a[10],b[10],c[10];  sprintf(a, "%d", 32);  sprintf(b, "%f", 3.1415);  sprintf(c, "%d", 567283);  printf("%s,%s,%s",a,b,c);  return 0;}Output:32,3.141500,567283

3. 使用stringstream进行字符串与数字的转换

例子4：

Example4// using stringstream constructors.#include <iostream>#include <sstream>using namespace std;int main () {  int a;float b;long c;  char d[10],e[10],f[10];  /* string to number */  stringstream ss;  ss << "32";  ss >> a;  ss.clear();  ss << "3.1415";  ss >> b;  ss.clear();  ss << "567283";  ss >> c;  ss.clear();  cout<<a<<","<<b<<","<<c<<endl;  /* number to string */  ss << a;  ss >> d;  ss.clear();  ss << b;  ss >> e;  ss.clear();  ss << c;  ss >> f;  ss.clear();  cout<<d<<","<<e<<","<<f<<endl;  return 0;}Output:32,3.141500,56728332,3.141500,567283

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