/*
--- Day 15: Chiton ---

You've almost reached the exit of the cave, but the walls are getting closer together. Your
submarine can barely still fit, though; the main problem is that the walls of the cave are covered
in chitons, and it would be best not to bump any of them.

The cavern is large, but has a very low ceiling, restricting your motion to two dimensions. The
shape of the cavern resembles a square; a quick scan of chiton density produces a map of risk level
throughout the cave (your puzzle input). For example:

```
1163751742
1381373672
2136511328
3694931569
7463417111
1319128137
1359912421
3125421639
1293138521
2311944581
```

You start in the top left position, your destination is the bottom right position, and you cannot
move diagonally. The number at each position is its risk level; to determine the total risk of an
entire path, add up the risk levels of each position you enter (that is, don't count the risk level
of your starting position unless you enter it; leaving it adds no risk to your total).

Your goal is to find a path with the lowest total risk. In this example, a path with the lowest
total risk is highlighted here:

```
1
1
2136511
      15
       1
       13
        2
        3
        21
         1
```

The total risk of this path is 40 (the starting position is never entered, so its risk is not
counted).

What is the lowest total risk of any path from the top left to the bottom right?
*/

package com.curtislb.adventofcode.year2021.day15.part1

import com.curtislb.adventofcode.year2021.day15.chiton.RiskLevelMap
import java.nio.file.Path
import java.nio.file.Paths

/**
 * Returns the solution to the puzzle for 2021, day 15, part 1.
 *
 * @param inputPath The path to the input file for this puzzle.
 */
fun solve(inputPath: Path = Paths.get("..", "input", "input.txt")): Long? {
    val riskLevelMap = RiskLevelMap.fromFile(inputPath.toFile())
    return riskLevelMap.findMinimalPathRisk()
}

fun main() {
    when (val solution = solve()) {
        null -> println("No solution")
        else -> println(solution)
    }
}
