Code Golf: Connecting the dots

Answer 1

Here goes!

#include 
#include 
#include 

int sign(int x) {
    if (x < 0)
        return -1;
    if (x > 0)
        return +1;
    return 0;
}

#define MAX_ROWS 100
#define MAX_COLS 100
#define MAX_DIGITS 100

int main(void)
{
    // Read in the digits
    int number[MAX_DIGITS][2];
    int rows = 0;
    int cols = 0;
    char row[MAX_COLS];
    int maxvalue = 0;
    int i, j, value, x;
    for (i = 0; i < MAX_ROWS; i++) {
        if (row != fgets(row, MAX_COLS, stdin))
            break;
        value = 0;
        for (j=0; row[j] != 0; j++) {
            if (row[j] >= '0' && row[j] <= '9') {
                x = j;
                value = 0;
                do {
                    value = 10*value + (row[j]-'0');
                    j++;
                } while (row[j] >= '0' && row[j] <= '9');
                number[value][0] = i;
                number[value][1] = x;
                if (maxvalue < value) maxvalue = value;
                if (rows < i+1) rows = i+1;
                if (cols < x+1) cols = x+1;
            }
        }
    }

    // Create an empty field
    char field[rows][cols];
    memset(field, ' ', rows*cols);

    char lines[] = "\\|/-+-/|\\";
    int dr,dc;
    // Draw the numbers and lines
    field[number[1][0]][number[1][1]] = '+';
    for (i = 2; i <= maxvalue; ++i) {
        int r = number[i-1][0];
        int c = number[i-1][1];
        int rt = number[i][0];
        int ct = number[i][1];
        dr = sign(rt-r);
        dc = sign(ct-c);
        char line = lines[(dr+1)*3+dc+1];
        while (r != rt || c != ct) {
            r += dr;
            c += dc;
            field[r][c] = line;
        }
        field[r][c] = '+';
    }

    for (i = 0; i < rows; ++i) {
        for (j = 0; j < cols; ++j)
            putchar(field[i][j]);
        putchar('\n');
    }

    return 0;
}