Store the numericals in char array into an INTEGER variable in VC++.

Question

My scenario is as follows:(C++)

In char a[10], the array a[] has elements (numbers) like '1','2','3' etc....

Say a[0] = '1';
a[1] = '2';
a[2] = '3';

Now a[] is storing 3 characters '1', '2' and '3'. I want to store this into an int as 123 (An integer 123).

How to achieve this in C++ ?

There is literally tons of stuff on string to int conversions all over SO and the internet. — chris, Jun 29 '12 at 09:46

score 4 · Accepted Answer · answered Jun 29 '12 at 09:44

4

a[3] = 0 is a must. If your string isn't null-terminated, most methods won't work.

After that, it's a simple number = atoi(a)

answered Jun 29 '12 at 09:44

SilverbackNet

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So, does it mean if I do a[3] = '\0'; explicitly then, i can simply assign "int number = atoi(a); ? – codeLover Jun 29 '12 at 09:50
Exactly. atoi() converts up to the first nul. – SilverbackNet Jun 29 '12 at 09:52
1

atoi() converts up to the first non digit (excluding any preceding whitespace and +/-) – SpacedMonkey Jun 29 '12 at 09:54

score 3 · Answer 2 · answered Jun 29 '12 at 09:44

3

Depending on what the value after a[2] is...

int total = 0;

for ( int i = 0; i < a[i]; i++ ) {
    total *= 10;
    total += a[i] - '0';
}

answered Jun 29 '12 at 09:44

SpacedMonkey

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Which is why I said, 'Depending on what the value after a[2] is' – SpacedMonkey Jun 29 '12 at 10:40
Yes, but `i < a[i]` does look extremely strange (it would be correct for 0-terminated arrays, though, didn't notice that originally). – Daniel Fischer Jun 29 '12 at 10:45

score 1 · Answer 3 · answered Jun 29 '12 at 09:50

#include <iostream>

int array2int(char a[]) {
  int i = 0;
  int value = 0;
  while (a[i]) {
    value *= 10; 
    value += a[i] - '0';
    i++;
  }
  return value;
};

int main(void) {
  char a[10] = "123";
  int value = array2int(a);
  std::cout << value << std::endl;
};

score 1 · Answer 4 · answered Jun 29 '12 at 11:37

1

#include <iostream>
int ca2int(char *array, size_t len){
    int v = 0;
    while(len--)
        v = 10*v + *array++ - '0';
    return v;
}

int main(){
    char a[10];
    a[0] = '1';
    a[1] = '2';
    a[2] = '3';

    std::cout << ca2int(a, 3);
}

answered Jun 29 '12 at 11:37

BLUEPIXY

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Store the numericals in char array into an INTEGER variable in VC++.

4 Answers4

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