Question

I need to read something like:

5 60 35 42
2 38 6
5 8
300 1500 900

And then save the first line in an array. After calling other functions do the same with the next line, and so on.

I try with gets() and then use sscanf() to scan the integers from the string, but I don’t know how to read n numbers from a string.

Answer 1

I’ve seen input files like this for competitions before. If speed is more of an issue than error detection, you could use a custom routine. Here’s one similar to that I use:

void readintline(unsigned int* array, int* size) {
    char buffer[101];
    size=0;
    char* in=buffer;
    unsigned int* out=array;
    fgets(buffer, 100, stdin);
    do {
        *out=0;
        while(*in>='0') {
            *out= *out* 10 + *in-'0';
            ++in;
        }
        if (*in)
            ++in; //skip whitespace
        ++out;
    } while(*in);
    size = out-array;
}

It will destroy your memory if there’s more than 100 characters on a line, or more numbers than array can hold, but you won’t get a faster routine to read in lines of unsigned ints.

On the other hand, if you want simple:

int main() {
    std::string tmp;
    while(std::getline(std::cin, tmp)) {
        std::vector<int> nums;
        std::stringstream ss(tmp);
        int ti;
        while(ss >> ti) 
            nums.push_back(ti);
        //do stuff with nums
    }
    return 0;
}