C/C++ 字串轉數字的方法

資料來源: https://shengyu7697.github.io/cpp-string-to-integer/

https://www.cplusplus.com/reference/cstdlib/strtol/

https://www.tutorialspoint.com/compile_c_online.php
https://www.tutorialspoint.com/compile_cpp_online.php

01.純C寫法:

#include <stdio.h>
#include <stdlib.h>
int main()
{
    char buffer[128] = "123";
    int integer = atoi(buffer);
    printf("str to int: %d\n", integer);
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
int main()
{
    char buffer[128] = "FF";
    char * pEnd;
    int integer = strtol(buffer,&pEnd,16);
    
    printf("str to int: %d\n", integer);

    printf("str to int: %o\n", integer);

    printf("str to int: %x\n", integer);

    return 0;
}

/* strtol example */
#include <stdio.h>      /* printf */
#include <stdlib.h>     /* strtol */

int main ()
{
  char szNumbers[] = "2001 60c0c0 -1101110100110100100000 0x6fffff";
  char * pEnd;
  long int li1, li2, li3, li4;
  li1 = strtol (szNumbers,&pEnd,10);
  li2 = strtol (pEnd,&pEnd,16);
  li3 = strtol (pEnd,&pEnd,2);
  li4 = strtol (pEnd,NULL,0);
  printf ("The decimal equivalents are: %ld, %ld, %ld and %ld.\n", li1, li2, li3, li4);
  return 0;
}

/*
The decimal equivalents are: 2001, 6340800, -3624224 and 7340031
*/

02.C++ 字串轉數字

#include <iostream>
#include <cstdlib>
using namespace std;

int main()
{
   cout << "Hello World" << endl; 
    char buffer[128] = "456";
    int integer = std::atoi(buffer);
    printf("str to int: %d\n", integer);   
   return 0;
}