diff options
| -rw-r--r-- | day3.zig | 235 |
1 files changed, 235 insertions, 0 deletions
diff --git a/day3.zig b/day3.zig new file mode 100644 index 0000000..b078f76 --- /dev/null +++ b/day3.zig @@ -0,0 +1,235 @@ +const std = @import("std"); +const Setup = @import("common.zig").Setup; + +pub fn main() !void { + // var setup = try Setup.get(); + // defer setup.deinit(); + try std.fmt.format(std.io.getStdOut().writer(), "day 3: {}\n", .{try solve(std.heap.page_allocator, input2)}); +} + +const Grid = struct { + buf: []const u8, + width: usize, + height: usize, + + fn init(input: []const u8) !Grid { + const height = std.mem.count(u8, input, "\n")+1; + const width = std.mem.indexOfScalar(u8, input, '\n') orelse return error.NoNewlines; + return .{ + .buf = input, + .width = width, + .height = height, + }; + } + fn get(self: Grid, x: usize, y: usize) ?u8 { + if (x >= self.width) return null; + if (y >= self.height) return null; + // width +1 becuase the buffer still has newlines in it + return self.buf[@intCast((self.width+1) * y + x)]; + } +}; + +fn solve(a: std.mem.Allocator, input: []const u8) !u32 { + var spanBuf = std.ArrayList(u8).init(a); + defer spanBuf.deinit(); + const grid = try Grid.init(input); + var sum: u32 = 0; + for (0..grid.height) |y| { + spanBuf.clearRetainingCapacity(); + for (0..grid.width) |x| { + const ch = grid.get(x, y) orelse return error.IndexError; + if (std.ascii.isDigit(ch)) { + try spanBuf.append(ch); + } + // end-of-span, either hit a non-digit or end of line + if ((!std.ascii.isDigit(ch) or (x==grid.width-1)) and spanBuf.items.len > 0) { + const num = try std.fmt.parseInt(u32, spanBuf.items, 10); + const num_len = spanBuf.items.len; + spanBuf.clearRetainingCapacity(); + // now check all the surrounding positions including diagonals, for non-digits and points + const search_x_end = x; + const search_x_start = std.math.sub(usize, search_x_end, (num_len+1)) catch search_x_end-num_len; + const is_part: bool = br: for (search_x_start..(search_x_end)+1) |x_p| { + const search_y_start = std.math.sub(usize, y, 1) catch y; + const search_y_end = y+1; + for (search_y_start..(search_y_end+1)) |y_p| { + if (grid.get(x_p, y_p)) |adj| { + if (!std.ascii.isDigit(adj) and adj != '.') { + //std.log.info("found symbol {c} next to num {}", .{adj, num}); + break :br true; + } + } + } + } else { + //std.log.info("no symbol next to num {}", .{num}); + break :br false; + }; + if (is_part) { + sum += num; + } + } + } + } + return sum; +} + + + +test { + const input = + \\467..114.. + \\...*...... + \\..35..633. + \\......#... + \\617*...... + \\.....+.58. + \\..592..... + \\......755. + \\...$.*.... + \\.664.598.. + ; + try std.testing.expectEqual(@as(u32, 4361), try solve(std.testing.allocator, input)); +} + +const input2 = +\\.......497...........................858...923...128..................227..801........487.....664........................................... +\\436........765..............140.......+....................859.............*.........+.................960........668....................... +\\...*982...........=..........=....203......266.263...375*....=...402....691..-....................*..........575....................13...... +\\.............114...588...............*............*......631........*.......952...463..14.......661..........=...706......*333.........595.. +\\...194.........*..............743...917.&......375.....................................*...............544*.......*....664.................. +\\...*.....807..452....81..........*......969..#......309*................/....873....941...828.197..........427.728...............566...13... +\\.243........*.....80.......329....470.......145.475.....111........*659..259....+........*....%........569..............%.....*....*....*... +\\.........130......*....385*............123......................199.......................640.....463..%.........978....920...266..380.83... +\\.....323........870.........+...........$.........466......453........................297...........*............*.......................... +\\........*.=..............588.....*786......$.........*........*.......390*.....886...*....227...728..852.......606....*863.......916..396... +\\.....538...287................301........133.....539..........33.537......466..$...793..+..........*...............218.....721........*..... +\\...............986.........=.......................................*...%...............222..-.......701.271...............#.........437..... +\\......*3.........*.626.68...419...740...........................806...976.......875.........174..............735.............=488........... +\\...790.........487....*................./532..13............................*....-.....503..........*11..734..........978.19......622....... +\\...................&....712.68=.619+.........*.......................863...596.....2.....*.......160.....+...&659........*.........-....-757 +\\437*.......#........520...*..........304....568.974.255.318.183.........*.......&.....675......................................849.......... +\\....161.....687.710.....854.............*.......*......*....&...441......891.....476..........616.......$........235..434.880...*..673+..... +\\..................*...............683.....800.120..............*....807..................................707.....*....-....*...74........562 +\\....@...#988...487..#685..........-......*..............251.146.............................142@....74...........398....769..........238*... +\\....848....../................-.$.....662.........773..*...........895.......591...........................233.............................. 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+\\....................*........*.......434.......796...........65............................................-479.126..*..............+....... +\\.....382..........121.....836.........*........@...............*789.......624........350&..........*544............$.6.........882....513... +\\....%.....406.........................848........625...%...88.........382..+..971.................5......*622...........914....*....%....... +\\..............627....816........641..............*.....373./.............*..../...912..651.162........557........901...&.....503.337....59.. +\\...357...........*.........552...*..816..........240......................636.....*...*.....*.............@..993....*....................... +\\......*934....961...=..43..*...324.....@...............726.888....370...........170.805...517........639.389....*..929.................953.. 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+\\967...................................25....234...........................306....281..........=..36..918.432....../406........344...$....... +\\.....700*610.......=...839......917......33......610@................537....=....@............................%........20.402.@.....926..... +\\..............%.768...*....................*...@............93..161.%...............74$......%.........96..298..........%..+............+519 +\\...........925.......586...................264..85...721....*...*.............................371.................822.=..................... +\\...............540...........-....447....................987.....305.............379@.707..............670...397...*..842....552.464........ +\\.....666......*....844....515.......*..............+114..............977...............&...393........*.........$.800...........*........... 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