Convert char array to single int? - c++

Question

Anyone know how to convert a char array to a single int?
char hello[5];
hello = "12345";
int myNumber = convert_char_to_int(hello);
Printf("My number is: %d", myNumber);

Answer 1

There are mulitple ways of converting a string to an int.
Solution 1: Using Legacy C functionality
int main()
{
//char hello[5];
//hello = "12345"; --->This wont compile
char hello[] = "12345";
Printf("My number is: %d", atoi(hello));
return 0;
}
Solution 2: Using lexical_cast(Most Appropriate & simplest)
int x = boost::lexical_cast<int>("12345");
Solution 3: Using C++ Streams
std::string hello("123");
std::stringstream str(hello);
int x;
str >> x;
if (!str)
{
// The conversion failed.
}

Answer 2

If you are using C++11, you should probably use stoi because it can distinguish between an error and parsing "0".
try {
int number = std::stoi("1234abc");
} catch (std::exception const &e) {
// This could not be parsed into a number so an exception is thrown.
// atoi() would return 0, which is less helpful if it could be a valid value.
}
It should be noted that "1234abc" is implicitly converted from a char[] to a std:string before being passed to stoi().

Answer 3

I use :
int convertToInt(char a[1000]){
int i = 0;
int num = 0;
while (a[i] != 0)
{
num = (a[i] - '0') + (num * 10);
i++;
}
return num;;
}

Answer 4

Use sscanf
/* sscanf example */
#include <stdio.h>
int main ()
{
char sentence []="Rudolph is 12 years old";
char str [20];
int i;
sscanf (sentence,"%s %*s %d",str,&i);
printf ("%s -> %d\n",str,i);
return 0;
}

Answer 5

I'll just leave this here for people interested in an implementation with no dependencies.
inline int
stringLength (char *String)
{
int Count = 0;
while (*String ++) ++ Count;
return Count;
}
inline int
stringToInt (char *String)
{
int Integer = 0;
int Length = stringLength(String);
for (int Caret = Length - 1, Digit = 1; Caret >= 0; -- Caret, Digit *= 10)
{
if (String[Caret] == '-') return Integer * -1;
Integer += (String[Caret] - '0') * Digit;
}
return Integer;
}
Works with negative values, but can't handle non-numeric characters mixed in between (should be easy to add though). Integers only.

Answer 6

For example, "mcc" is a char array and "mcc_int" is the integer you want to get.
char mcc[] = "1234";
int mcc_int;
sscanf(mcc, "%d", &mcc_int);

Answer 7

With cstring and cmath:
int charsToInt (char* chars) {
int res{ 0 };
int len = strlen(chars);
bool sig = *chars == '-';
if (sig) {
chars++;
len--;
}
for (int i{ 0 }; i < len; i++) {
int dig = *(chars + i) - '0';
res += dig * (pow(10, len - i - 1));
}
res *= sig ? -1 : 1;
return res;
}

Answer 8

Ascii string to integer conversion is done by the atoi() function.

Answer 9

Long story short you have to use atoi()
ed:
If you are interested in doing this the right way :
char szNos[] = "12345";
char *pNext;
long output;
output = strtol (szNos, &pNext, 10); // input, ptr to next char in szNos (null here), base