Day 10 Mark

day 10/day_10_mark.js

+heights = input.split("\n").map(x => x.split('').map(Number))
+n = heights.length
+m = heights[0].length
+
+range = x => [...Array(x).keys()]
+
+isValid = x => (x[0] >= 0 && x[0] < n && x[1] >= 0 && x[1] < m)
+
+trailheads = []
+trailends = []
+range(n).map(i => range(m).map(j => heights[i][j] == 0 ? trailheads.push([i,j]) : (heights[i][j] == 9 ? trailends.push([i,j]) : undefined)))
+
+neighbours = x => [[x[0]-1,x[1]],[x[0]+1,x[1]],[x[0],x[1]-1],[x[0],x[1]+1]].filter(isValid)
+
+getEntry = x => isValid(x) ? heights[x[0]][x[1]] : undefined
+setEntry = (x,y) => isValid(x) ? heights[x[0]][x[1]] = y : undefined
+
+onlyUnique = (v, i, a) => a.map(x => x.toString()).indexOf(v.toString()) === i
+
+output1 = trailheads.reduce((t,x) => {
+	level = 1
+	list = [x]
+	while(level < 10){
+		newList = []
+		list.map(y => newList = newList.concat(neighbours(y).filter(z => getEntry(z) == level)))
+		list = newList
+		level++
+	}
+	return t + trailends.reduce((y,z) => y + list.map(x => x.toString()).includes(z.toString()), 0)
+}, 0)
+
+output2 = trailheads.reduce((t,x) => {
+	level = 1
+	list = [x]
+	paths = {}
+	paths[x.toString()] = 1
+	while(level < 10){
+		newList = []
+		list.map(y => {
+			neighbourhood = neighbours(y).filter(z => getEntry(z) == level)
+			newList = newList.concat(neighbourhood)
+			neighbourhood.map(z => paths[z.toString()] ? paths[z.toString()] += paths[y.toString()] : paths[z.toString()] = paths[y.toString()])
+		})
+		list = newList.filter(onlyUnique)
+		level++
+	}
+	return t + trailends.reduce((y,z) => y + (paths[z.toString()] ? paths[z.toString()] : 0),0)
+},0)
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