数字转为 string
std::to_string() 函数
// Defined in header <string>
std::string to_string(int value); // (since C++11)
std::string to_string(long value); // (since C++11)
std::string to_string(long long value); // (since C++11)
std::string to_string(unsigned value); // (since C++11)
std::string to_string(unsigned long value); // (since C++11)
std::string to_string(unsigned long long value); // (since C++11)
std::string to_string(float value); // (since C++11)
std::string to_string(double value); // (since C++11)
std::string to_string(long double value); // (since C++11)
example:
#include <iostream>
#include <string>
int main()
{
int i = 23;
std::string str = std::to_string(i); // 把 i 转为 string 并赋值给 str
std::cout << str << std::endl; // str = "23"
}
stringstream 类
example:
#include <iostream>
#include <string>
#include <sstream>
int main()
{
int a = 10;
std::stringstream ss;
ss << a;
std::string str = ss.str(); // str = "10"
std::cout << str << std::endl;
}
springf()
把数字转为 char*, 再转为string。
int sprintf( char* buffer, const char* format, ... );
example:
#include <iostream>
#include <string>
#include <cstdio>
int main()
{
int i = 23;
char* buf = (char*)malloc(20); // 分配内存
std::sprintf(buf, "%d", i);
std::string str = std::string(buf);
std::cout << str << std::endl; // str = "23"
}
string 转为数字
unsigned long stoul(const std::string& str, std::size_t* pos = nullptr, int base = 10);
unsigned long long stoull( const std::string& str, std::size_t* pos = nullptr, int base = 10 );
int stoi( const std::string& str, std::size_t* pos = nullptr, int base = 10 );
long stol( const std::string& str, std::size_t* pos = nullptr, int base = 10 );
long long stoll( const std::string& str, std::size_t* pos = nullptr, int base = 10 );
float stof( const std::string& str, std::size_t* pos = nullptr );
double stod( const std::string& str, std::size_t* pos = nullptr );
long double stold( const std::string& str, std::size_t* pos = nullptr );
example:
#include <iostream>
#include <string>
#include <cstdio>
using namespace std;
int main()
{
string str = "-123.556";
unsigned long u = stoul(str); // u = 4294967173; 应该是先转为 32 位带符号的整型,再转为 unsigned long
unsigned long long lu = stoull(str); // lu = 18446744073709551493; 转为 64 位带符号的整型,再转为无符号的
int i = stoi(str); // i = -123
float f = stof(str); // f = -123.556
}