C - Adding the numbers in 2 strings together if a different length

Question

If I had two strings:

a = \"1234\"
b = \"4321\"

I could add the two numbers together like this:

for(i=0; i

        

Answer 1

int getcharval(const char *s, int idx) {
    if (idx < strlen(s))
        return s[strlen(s) - idx - 1] - 48; 
    return 0;
}

void add() {
    const char *a = "1234";
    const char *b = "13210";
    char answer[256];
    int i, wa=strlen(a), wb=strlen(b), width, sum, carry;
    width = wa > wb ? wa : wb; 
    for(i=0; i 9){ 
            carry = 1;
            sum-=10;
        }
        answer[i] = sum+48;
    }   
    if(carry) answer[i++] = carry+48;
    answer[i]= 0;
    for (i = 0; i < strlen(answer) / 2; i++) {
        char t = answer[i];
        answer[i] = answer[strlen(answer) - i - 1]; 
        answer[strlen(answer) - i - 1] = t;
    }   

    printf("%s\n", answer);
}