You are given a sorted list of unique positive integers.
Write a script to return list of arrays where the arrays are consecutive integers.
Input: (1, 2, 3, 6, 7, 8, 9)
Output: ([1, 2, 3], [6, 7, 8, 9])
Input: (11, 12, 14, 17, 18, 19)
Output: ([11, 12], [14], [17, 18, 19])
Input: (2, 4, 6, 8)
Output: ([2], [4], [6], [8])
Input: (1, 2, 3, 4, 5)
Output: ([1, 2, 3, 4, 5])
We will be reading the array from standard input, with all the numbers on the same line. We will be writing each array to a different line of standard output.
We will be iterating over the numbers, keeping the previous processed
number in a variable prev, which we initialize to 0. For each number
we first print a separator, then the number. The separator printed
depends on the previous and current number:
prev is 0, we use the empty string as separator (this only happens
for the first number).prev is one less than the current number, we use a space as
separator (as it belongs to the same array as the previous number
belongs to)With the input array in $_, and having $prev initialized to 0,
the gist of the program is just a one liner:
print $prev ? $prev + 1 == $_ ? " " : "\n" : "", $prev = $_ for /[0-9]+/g
Find the full program on GitHub.
The AWK solution is quite similar. AWK auto splits the input on white
space, making each field available in variables $1, $2, etc.
{
prev = 0
for (i = 1; i <= NF; i ++) {
printf ("%s%d", prev == 0 ? "" : (prev + 1 == $i) ? " " : "\n",
(prev = $i))
}
printf ("\n")
}
Find the full program on GitHub.
In C, we use sscanf to extract the numbers from a given string,
then follow the same steps we used in our Perl and AWK solutions.
Here, we have the line of input in variable line_ptr:
int num;
int offset;
int prev = 0;
while (sscanf (line_ptr, "%d%n", &num, &offset) == 1) {
printf ("%s%d", prev == 0 ? ""
: prev + 1 == num ? " "
: "\n", num);
prev = num;
line_ptr += offset;
}
printf ("\n");
Find the full program on GitHub.