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Solve day 9

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This commit is contained in:
Tyler Hallada 2022-12-10 15:01:41 -05:00
parent d03e2f28da
commit 2f485e9dbc
2 changed files with 64 additions and 51 deletions
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67
src/day09.zig
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@ -2,69 +2,73 @@ const std = @import("std");
pub const input = @embedFile("input/day09.txt");
const test_input1 = @embedFile("input/day09_test1.txt");
const test_input2 = @embedFile("input/day09_test2.txt");
var gpa = std.heap.GeneralPurposeAllocator(.{ .safety = true }){};
const allocator = gpa.allocator();
pub fn solve_part1(data: []const u8) !usize {
var lines = std.mem.tokenize(u8, data, "\n");
var visited = std.AutoHashMap([2]isize, void).init(allocator);
var head = [2]isize{ 0, 0 };
var tail = [2]isize{ 0, 0 };
try visited.put(tail, {});
while (lines.next()) |line| {
fn move_rope(comptime S: usize, knots: *[S][2]isize, line: []const u8, visited: *std.AutoHashMap([2]isize, void)) !void {
const direction = line[0];
const steps = try std.fmt.parseInt(u8, line[2..], 10);
// std.debug.print("{s} {d}\n", .{ [_]u8{direction}, steps });
var step: usize = 0;
while (step < steps) : (step += 1) {
// std.debug.print("move head: {s}\n", .{[_]u8{direction}});
switch (direction) {
'R' => {
head[0] += 1;
knots[0][0] += 1;
},
'L' => {
head[0] -= 1;
knots[0][0] -= 1;
},
'U' => {
head[1] -= 1;
knots[0][1] -= 1;
},
'D' => {
head[1] += 1;
knots[0][1] += 1;
},
else => unreachable,
}
var x_diff = tail[0] - head[0];
var y_diff = tail[1] - head[1];
// std.debug.print("x_diff: {d}\n", .{x_diff});
// std.debug.print("y_diff: {d}\n", .{y_diff});
var i: usize = 1;
while (i < knots.len) : (i += 1) {
var x_diff = knots[i][0] - knots[i - 1][0];
var y_diff = knots[i][1] - knots[i - 1][1];
if (x_diff < -1 or x_diff > 1 or y_diff < -1 or y_diff > 1) {
if (x_diff < 0) {
// std.debug.print("move tail x: {d}\n", .{-1});
tail[0] += 1;
knots[i][0] += 1;
} else if (x_diff > 0) {
// std.debug.print("move tail x: {d}\n", .{1});
tail[0] -= 1;
knots[i][0] -= 1;
}
if (y_diff < 0) {
// std.debug.print("move tail y: {d}\n", .{-1});
tail[1] += 1;
knots[i][1] += 1;
} else if (y_diff > 0) {
// std.debug.print("move tail y: {d}\n", .{1});
tail[1] -= 1;
knots[i][1] -= 1;
}
try visited.put(tail, {});
if (i == knots.len - 1) try visited.put(knots[i], {});
}
// std.debug.print("head: {d}\n", .{head});
// std.debug.print("tail: {d}\n", .{tail});
}
}
}
pub fn solve_part1(data: []const u8) !usize {
var lines = std.mem.tokenize(u8, data, "\n");
var visited = std.AutoHashMap([2]isize, void).init(allocator);
var knots = [2][2]isize{ [2]isize{ 0, 0 }, [2]isize{ 0, 0 } };
try visited.put(knots[0], {});
while (lines.next()) |line| {
try move_rope(2, &knots, line, &visited);
}
return visited.count();
}
pub fn solve_part2(data: []const u8) !usize {
_ = data;
return 0;
var lines = std.mem.tokenize(u8, data, "\n");
var visited = std.AutoHashMap([2]isize, void).init(allocator);
var knots = [_][2]isize{[_]isize{ 0, 0 }} ** 10;
try visited.put(knots[0], {});
while (lines.next()) |line| {
try move_rope(10, &knots, line, &visited);
}
return visited.count();
}
test "solves part1" {
@ -72,5 +76,6 @@ test "solves part1" {
}
test "solves part2" {
try std.testing.expectEqual(solve_part2(test_input1), 0);
try std.testing.expectEqual(solve_part2(test_input1), 1);
try std.testing.expectEqual(solve_part2(test_input2), 36);
}

8
src/input/day09_test2.txt Normal file
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@ -0,0 +1,8 @@
R 5
U 8
L 8
D 3
R 17
D 10
L 25
U 20