mirror of
https://github.com/Threnklyn/advent-of-code-go.git
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day 10 part 2
This commit is contained in:
alexchao26
+155
-44
@@ -71,46 +71,30 @@ func pipeMaze(input string, part int) int {
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}
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}
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// need to find which directions are connected to the initial cell
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// could traverse along the four directions and see which two lead back to
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// the start... all pipes only connect two coordinates so it's actually
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// fairly easy to traverse without creating a huge search space
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fillGridLocation(grid, r, c)
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// note this soultion was overkill for part 1
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// inputs are nice and exactly two adjacent cells that connect to S
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var loopCoords map[[2]int]bool
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for pipeType := range pipes {
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// assign the start square to a random pipeType, then see if it will loop
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grid[r][c] = pipeType
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seen := map[[2]int]bool{}
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toAnalyze := [][2]int{
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{r, c},
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}
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didLoop := false
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for len(toAnalyze) > 0 {
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coords := toAnalyze[0]
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if seen[coords] {
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didLoop = true
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break
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}
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seen[coords] = true
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toAnalyze = toAnalyze[1:]
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if diffs, ok := pipes[grid[coords[0]][coords[1]]]; ok {
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for _, diff := range diffs {
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nextRow, nextCol := coords[0]+diff[0], coords[1]+diff[1]
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if isInRange(grid, nextRow, nextCol) && !seen[[2]int{nextRow, nextCol}] {
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toAnalyze = append(toAnalyze, [2]int{nextRow, nextCol})
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}
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}
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}
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}
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if didLoop {
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loopCoords = seen
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// traverse entire loop to determine length
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loopCoords := map[[2]int]bool{}
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toVisit := [][2]int{
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{r, c},
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}
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for len(toVisit) > 0 {
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coords := toVisit[0]
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if loopCoords[coords] {
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break
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}
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loopCoords[coords] = true
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toVisit = toVisit[1:]
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// assumes loop is well formed, will cause a panic if not
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diffs := pipes[grid[coords[0]][coords[1]]]
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for _, diff := range diffs {
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nextRow, nextCol := coords[0]+diff[0], coords[1]+diff[1]
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if isInRange(grid, nextRow, nextCol) && !loopCoords[[2]int{nextRow, nextCol}] {
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toVisit = append(toVisit, [2]int{nextRow, nextCol})
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}
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}
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}
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if part == 1 {
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@@ -119,26 +103,153 @@ func pipeMaze(input string, part int) int {
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// part 2
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newGrid := make([][]string, len(grid))
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// create copy of grid with all non-loop spots replaced with a period
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reducedGrid := make([][]string, len(grid))
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for i := 0; i < len(grid); i++ {
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for j := 0; j < len(grid[0]); j++ {
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if loopCoords[[2]int{i, j}] {
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newGrid[i] = append(newGrid[i], grid[i][j])
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reducedGrid[i] = append(reducedGrid[i], grid[i][j])
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} else {
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newGrid[i] = append(newGrid[i], ".")
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reducedGrid[i] = append(reducedGrid[i], ".")
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}
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}
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}
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for _, r := range newGrid {
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fmt.Println(r)
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// expand grid to double plus 2 in both dimensions to account for squeezing between pipes
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// the plus two is to add an empty row/column on each side for easier traversing from the outside
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expandedGrid := [][]string{}
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expandedGrid = append(expandedGrid, make([]string, len(reducedGrid[0])*2+2))
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for r, rows := range reducedGrid {
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expandedGrid = append(expandedGrid, make([]string, len(reducedGrid[0])*2+2))
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for c, val := range rows {
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expandedGrid[r*2+1][c*2+1] = val
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}
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// empty row
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expandedGrid = append(expandedGrid, make([]string, len(reducedGrid[0])*2+2))
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}
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return -1
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// fill gaps between loop coords so we have an encased area again
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// we can naively try to fill in every empty spot because only ones with two valid connecting
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// pipes will be filled
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for r, rows := range expandedGrid {
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for c, val := range rows {
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if val == "" {
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fillGridLocation(expandedGrid, r, c)
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}
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}
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}
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// replacing empty strings with spaces makes the printout human readable
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for r, rows := range expandedGrid {
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for c, val := range rows {
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if val == "" {
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expandedGrid[r][c] = " "
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}
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}
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}
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toVisit = [][2]int{
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{0, 0},
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}
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seen := map[[2]int]bool{}
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for len(toVisit) > 0 {
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coords := toVisit[0]
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toVisit = toVisit[1:]
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if seen[coords] {
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continue
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}
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seen[coords] = true
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// delete reachable dots
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if expandedGrid[coords[0]][coords[1]] == "." {
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expandedGrid[coords[0]][coords[1]] = " "
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}
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for _, diff := range [][2]int{
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{-1, 0},
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{1, 0},
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{0, -1},
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{0, 1},
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} {
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nextRow := coords[0] + diff[0]
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nextCol := coords[1] + diff[1]
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if isInRange(expandedGrid, nextRow, nextCol) {
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if expandedGrid[nextRow][nextCol] == "." || expandedGrid[nextRow][nextCol] == " " {
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toVisit = append(toVisit, [2]int{nextRow, nextCol})
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}
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}
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}
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}
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// count remaining dots
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var ans int
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for _, rows := range expandedGrid {
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for _, val := range rows {
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if val == "." {
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ans++
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}
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}
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}
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// for _, rows := range expandedGrid {
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// fmt.Println(rows)
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// }
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return ans
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}
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func fillGridLocation(grid [][]string, r, c int) {
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// inputs are nice and exactly two adjacent cells that connect to S
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// check four directions from start
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leftCol := c - 1
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rightCol := c + 1
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upRow := r - 1
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downRow := r + 1
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var combinedString string
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// check left for inRange and possible valid pipe types
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if isInRange(grid, r, leftCol) &&
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(grid[r][leftCol] == "-" || grid[r][leftCol] == "L" || grid[r][leftCol] == "F") {
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combinedString += "left"
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}
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// right
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if isInRange(grid, r, rightCol) &&
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(grid[r][rightCol] == "-" || grid[r][rightCol] == "J" || grid[r][rightCol] == "7") {
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combinedString += "right"
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}
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// up
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if isInRange(grid, upRow, c) &&
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(grid[upRow][c] == "|" || grid[upRow][c] == "7" || grid[upRow][c] == "F") {
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combinedString += "up"
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}
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if isInRange(grid, downRow, c) &&
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(grid[downRow][c] == "|" || grid[downRow][c] == "J" || grid[downRow][c] == "L") {
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combinedString += "down"
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}
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switch combinedString {
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case "leftup":
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grid[r][c] = "J"
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case "leftdown":
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grid[r][c] = "7"
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case "rightup":
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grid[r][c] = "L"
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case "rightdown":
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grid[r][c] = "F"
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case "leftright":
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grid[r][c] = "-"
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case "updown":
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grid[r][c] = "|"
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// default:
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// do not panic so we can use this function more naively for the expanded grid
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// could return an error instead and choose to check it for part1 where we NEED it to find a result
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// panic("ineligible configuration: " + combinedString)
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}
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}
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func isInRange(grid [][]string, row, col int) bool {
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return row >= 0 && row < len(grid) && col >= 0 && col <= len(grid)
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return row >= 0 && row < len(grid) && col >= 0 && col < len(grid[0])
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}
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func parseInput(input string) (ans [][]string) {
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@@ -106,12 +106,12 @@ func Test_pipeMaze(t *testing.T) {
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part: 2,
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want: 10,
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},
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// {
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// name: "actual part 2",
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// input: input,
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// part: 2,
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// want: 0,
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// },
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{
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name: "actual part 2",
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input: input,
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part: 2,
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want: 493,
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},
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}
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for _, tt := range tests {
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t.Run(tt.name, func(t *testing.T) {
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