Sum of Integers in a String C

Question

This is my first time using pointers, which is why my logic is probably very flawed. I am writing a program that sums up numbers in a string using atoi(). For example, sumNumbers("1 2 b asdsd 3 4) should be 10. Here is my program,

int sumString(char string[]) {
    char *ptr=string;
    int index = 0;
    int len = strlen(string);
    int sum = 0;
    while(index < len) {
        while (ptr[0] == ' ') {
            ptr++;
            index++;
            if (index == len) {
                return sum;
            } 
        }
        while (atoi(ptr) == 0) {
            ptr++;
            index++;
            if (index == len) {
                return sum;
            }
        }
        if (atoi(ptr) != 0) {
            sum += atoi(ptr);
            ptr++;
            index++;
            while (ptr[0] != ' ' || atoi(ptr) != 0 || ptr[0] == '\0') {
                ptr++;
                index++;
            }
        }
    }
    return sum;
}

My first conditional should get rid of all white spaces, my second should keep running for all letters, and my third should add up the value of atoi, keep going until a space or a letter, and then the loop should iterate again and the first two conditionals perform their tasks again. Unfortunately, this works for most cases except if I glue a letter to a number, like "18b5". This should return 23, but it returns 18 instead.

[Don't use atoi()?](https://stackoverflow.com/q/17710018/995714) — phuclv, Nov 03 '17 at 03:59
Use [strtol](http://en.cppreference.com/w/c/string/byte/strtol) like [this](https://ideone.com/8IKrcK) — BLUEPIXY, Nov 03 '17 at 05:58

score 0 · Answer 1 · answered Nov 03 '17 at 03:55

0

Apparently, my one problem was that my last while loop should have had && instead of || between the first two statements.

answered Nov 03 '17 at 03:55

DrJessop

462
6
26

I'm pretty surprised this works actually, the case for handling an integer ( while (ptr[0] != ' ' || atoi(ptr) != 0 || ptr[0] == '\0') ) seems a little iffy to me. EDIT: oh right that's what you just said – information_interchange Nov 03 '17 at 03:57
what output should expect if the string is "1234" ? should be 10 right ? – ntshetty Nov 03 '17 at 04:09
No, the output should be 1234 in that case. – DrJessop Nov 03 '17 at 04:23

score 0 · Accepted Answer · answered Nov 03 '17 at 03:57

0

The last loop should be changed to:

        while (ptr[0] != '\0' && atoi(ptr) != 0) {
            ptr++;
            index++;
        }

answered Nov 03 '17 at 03:57

iamnoten

231
2
7

Sum of Integers in a String C

2 Answers2