advent-of-code-2021/10/solve.zig

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2021-12-10 06:26:12 +00:00
const std = @import("std");
const Pair = struct {
opening: u8,
closing: u8,
score: u32,
};
const pairs = [4]Pair{
Pair{
.opening = '(',
.closing = ')',
.score = 3,
},
Pair{
.opening = '[',
.closing = ']',
.score = 57,
},
Pair{
.opening = '{',
.closing = '}',
.score = 1197,
},
Pair{
.opening = '<',
.closing = '>',
.score = 25137,
},
};
pub fn main() !void {
var alloc = std.heap.GeneralPurposeAllocator(.{}){};
defer std.debug.assert(!alloc.deinit());
var gpa = &alloc.allocator;
const stdin = std.io.getStdIn().reader();
var res: u32 = 0;
var scores = std.ArrayList(u64).init(gpa);
defer scores.deinit();
var tmp: [256]u8 = undefined;
while (try stdin.readUntilDelimiterOrEof(&tmp, '\n')) |line| {
var stack = std.ArrayList(u8).init(gpa);
defer stack.deinit();
var corrupt = false;
for (line) |char| {
for (pairs) |pair| {
if (char == pair.opening) {
try stack.append(char);
}
if (char == pair.closing) {
var matching = stack.pop();
if (matching != pair.opening) {
res += pair.score;
corrupt = true;
}
}
}
}
if (!corrupt and stack.items.len > 0) {
var score: u64 = 0;
std.mem.reverse(u8, stack.items);
for (stack.items) |char| {
score *= 5;
for (pairs) |pair, i| {
if (char == pair.opening) {
score += (@intCast(u64, i) + 1);
}
}
}
try scores.append(score);
}
}
std.sort.sort(u64, scores.items, {}, comptime std.sort.asc(u64));
var middleScore = scores.items[@divFloor(scores.items.len, 2)];
std.debug.print("{}\n", .{res});
std.debug.print("{}\n", .{middleScore});
}