part1 (1853B)
1--- Day 5: Hydrothermal Venture --- 2 3You come across a field of hydrothermal vents on the ocean floor! These vents constantly produce 4large, opaque clouds, so it would be best to avoid them if possible. 5 6They tend to form in [1m[37mlines[0m; the submarine helpfully produces a list of nearby lines of vents (your 7puzzle input) for you to review. For example: 8 90,9 -> 5,9 108,0 -> 0,8 119,4 -> 3,4 122,2 -> 2,1 137,0 -> 7,4 146,4 -> 2,0 150,9 -> 2,9 163,4 -> 1,4 170,0 -> 8,8 185,5 -> 8,2 19 20Each line of vents is given as a line segment in the format x1,y1 -> x2,y2 where x1,y1 are the 21coordinates of one end the line segment and x2,y2 are the coordinates of the other end. These line 22segments include the points at both ends. In other words: 23 24 25 - An entry like 1,1 -> 1,3 covers points 1,1, 1,2, and 1,3. 26 27 - An entry like 9,7 -> 7,7 covers points 9,7, 8,7, and 7,7. 28 29 30For now, [1m[37monly consider horizontal and vertical lines[0m: lines where either x1 = x2 or y1 = y2. 31 32So, the horizontal and vertical lines from the above list would produce the following diagram: 33 34.......1.. 35..1....1.. 36..1....1.. 37.......1.. 38.112111211 39.......... 40.......... 41.......... 42.......... 43222111.... 44 45In this diagram, the top left corner is 0,0 and the bottom right corner is 9,9. Each position is 46shown as [1m[37mthe number of lines which cover that point[0m or . if no line covers that point. The top-left 47pair of 1s, for example, comes from 2,2 -> 2,1; the very bottom row is formed by the overlapping 48lines 0,9 -> 5,9 and 0,9 -> 2,9. 49 50To avoid the most dangerous areas, you need to determine [1m[37mthe number of points where at least two 51lines overlap[0m. In the above example, this is anywhere in the diagram with a 2 or larger - a total of 52[1m[37m5[0m points. 53 54Consider only horizontal and vertical lines. [1m[37mAt how many points do at least two lines overlap?[0m 55 56