string to individual numbers

Question

I ran across a problem where I need to extract each element of string to an integer array, the string only contains integer values without any space or delimiter.

Here is an example.

char input[8]="02320000";

to

int output[8]={0,2,3,2,0,0,0,0};

I tried to use the atoi() and it is taking the entire string as digit.

The string characters will be 0-3.

thank you

Do you know how to deal with individual characters in strings? — user253751, Jan 30 '18 at 01:03
atoi() converts the string to a single integer, not an array of integers. — Cpp plus 1, Jan 30 '18 at 01:04

score 3 · Answer 1 · answered Jan 30 '18 at 01:06

3

char input[8]="02320000";
int output[8];

for(int i = 0; i < 8; i++)
{
     output[i] = input[i] - '0';
}

explanation of the -'0' Convert a character digit to the corresponding integer in C

answered Jan 30 '18 at 01:06

pm100

48,078
23
82
145

This got me thinking about end of string and char array initialization, so I played with it a little bit. I learned that "02320000" seems to get implicitly cast to either (char [8]) or (char [9]) depending on whether input is char input[8] or char input[9]. I didn't expect a size of both 8 and 9 to work as seamlessly as it did. For 8, it does not terminate the string, for 9, it does. Of course you can't use anything smaller than 8 for the array size. – Stephen Docy Jan 30 '18 at 01:45

Pablo · Accepted Answer · 2018-01-30T01:14:43.410

Well, you can loop through all characters of the string:

char input[8]="02320000";
char output[8];

for(int = 0; i < 8; ++i)
    output[i] = input[i] - '0';

Strings in C are just sequences of characters that ends with the so called '\0'-terminating byte, whose value is 0. We use char arrays to store them and we use the ASCII values for the character.

Note that 1 != '1'. 1 is the interger one, '1' is the representation of the number one. The representation has the value 49 (see ASCII). If you want to calculate the real number of a character representation, you have to use c-'0', where c is the character in question. That works because in the table, the values of the numbers also are ordered as the numbers themselves: '0' is 48, '1' is 49, '2' is 50, etc.

string to individual numbers

2 Answers2