finding sum of numbers in a char array - c++

Question

I'm trying to find the sum of the numbers in a char array.
My code works for most cases. Example : a=dasn344wee22ee, the output is:366 - which is good
But when my char is,for example : andre54e5 the output should be 59, but the program displays: 108.
Can anybody tell me what the issue is?
#include <iostream>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
using namespace std;
int getnr(char a[], int i, int j)
{
int counter = 0;
char sir[1000];
for (int x = i; x<j; x++)
{
sir[counter] = a[x];
counter++;
}
return atoi(sir);
}
int main()
{
char a[1000];
int s = 0, inceput, finals;
cin.getline(a, 255);
for (int i = 0; i<strlen(a); i++)
{
if (isdigit(a[i]) )
{
if (i == strlen(a) - 1)
{
s += getnr(a, i, strlen(a));
}
for (int j = i + 1; j<strlen(a); j++)
{
if (!isdigit(a[j]) || j == strlen(a) - 1)
{
s += getnr(a, i, j + 1);
i = j;
break;
}
}
}
}
cout << s;
return 0;
}

Answer 1

In your function int getnr(char a[], int i, int j), you forgot to null-terminate string sir, such that atoi(sir) might yield a garbage value (actually the behaviour is undefined). The following should help:
int getnr(char a[], int i, int j)` {
...
sir[counter] = '\0';
return atoi(sir);
}

Answer 2

The problem is that getnr() doesn't add a null terminator to the sir array, so you're getting undefined behavior when you call atoi(sir).
int getnr(char a[], int i, int j)
{
int counter = 0;
char sir[1000];
for (int x = i; x<j; x++)
{
sir[counter] = a[x];
counter++;
}
sir[counter] = '\0';
return atoi(sir);
}

Answer 3

The issue is within this part of code:
if (i == strlen(a) - 1)
{
s += getnr(a, i, strlen(a));
}
Specifically, if your last number is a single digit (which it is), it will always return junk.
So, I would change to only convert the single char of the char array as a digit and at it to the int s.
Edit:
For some reason when doing s+= a[i], I return junk.
But, doing the following, does the trick:
if (i == strlen(a) - 1)
{
string x;
x[0] = a[i];
int l = stoi(x);
s += l;
}
I know that there's a much more effective way, but I'm not sure why s+= a[i] itself returns false numbers.