/*
--- Part Two ---

Next, you need to find the largest basins so you know what areas are most important to avoid.

A basin is all locations that eventually flow downward to a single low point. Therefore, every low
point has a basin, although some basins are very small. Locations of height 9 do not count as being
in any basin, and all other locations will always be part of exactly one basin.

The size of a basin is the number of locations within the basin, including the low point. The
example above has four basins.

The top-left basin, size 3:

```
21........
3.........
..........
..........
..........
```

The top-right basin, size 9:

```
.....43210
......4.21
.........2
..........
..........
```

The middle basin, size 14:

```
..........
..878.....
.85678....
87678.....
.8........
```

The bottom-right basin, size 9:

```
..........
..........
.......8..
......678.
.....65678
```

Find the three largest basins and multiply their sizes together. In the above example, this is 9 *
14 * 9 = 1134.

What do you get if you multiply together the sizes of the three largest basins?
*/

package com.curtislb.adventofcode.year2021.day09.part2

import com.curtislb.adventofcode.common.comparison.takeLargest
import com.curtislb.adventofcode.common.number.product
import com.curtislb.adventofcode.year2021.day09.basin.HeightMap
import java.nio.file.Path
import java.nio.file.Paths

/**
 * Returns the solution to the puzzle for 2021, day 9, part 2.
 *
 * @param inputPath The path to the input file for this puzzle.
 * @param basinCount How many of the largest basin sizes should be multiplied to get the result.
 */
fun solve(inputPath: Path = Paths.get("..", "input", "input.txt"), basinCount: Int = 3): Int {
    val heightMap = HeightMap(inputPath.toFile().readText())
    return heightMap.findBasinSizes().takeLargest(basinCount).product()
}

fun main() {
    println(solve())
}
