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    "### Advent of Code 2022\n",
    "#### Day 4: Camp Cleanup\n",
    "\n",
    "Each elf in a pair of elves is assigned a range of ID numbers.\n",
    "\n",
    "**Part 1.** How many pairs have one elf assigned to a range completely contained by the other's?\n",
    "\n",
    "**Part 2.** How many pairs have overlapping assignments?\n",
    "\n",
    "Since this problem heavily uses ranges, I'm using `rebellion/base/range` to do the heavy lifting."
   ]
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   "source": [
    "#lang iracket/lang #:require rackjure\n",
    "(require advent-of-code\n",
    "         relation\n",
    "         rebellion/base/range)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##### Part 1\n",
    "\n",
    "All the assignments look like `\"11-22,33-44\"`, so we write a function to extract the numbers from the string with a regex, decompose the values with structural matching, and construct a pair of [`rebellion` ranges](https://docs.racket-lang.org/rebellion/Ranges.html).\n",
    "\n",
    "Once we have the two ranges, we can use a predicate that tests if one completely contains the other or vice versa to count the corresponding assignments."
   ]
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       "<code>550</code>"
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       "550"
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   "source": [
    "(define assignments (~> (fetch-aoc-input (find-session) 2022 4) string-split))\n",
    "\n",
    "(define (parse-range str)\n",
    "  (match str\n",
    "    [(regexp #px\"(\\\\d+)-(\\\\d+),(\\\\d+)-(\\\\d+)\" (list _ a b c d))\n",
    "     (values (closed-range (->number a) (->number b)) (closed-range (->number c) (->number d)))]))\n",
    "\n",
    "(define (one-encloses-the-other? str)\n",
    "  (define-values (range1 range2) (parse-range str))\n",
    "  (or (range-encloses? range1 range2) (range-encloses? range2 range1)))\n",
    "\n",
    "(count one-encloses-the-other? assignments)\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##### Part 2\n",
    "\n",
    "The procedure for part 2 is the same, just using the predicate for overlapping ranges instead."
   ]
  },
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   "execution_count": 3,
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       "<code>931</code>"
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       "931"
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   "source": [
    "(define (one-overlaps-the-other? str)\n",
    "  (define-values (range1 range2) (parse-range str))\n",
    "  (range-overlaps? range1 range2))\n",
    "\n",
    "(count one-overlaps-the-other? assignments)\n"
   ]
  }
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