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const std = @import("std");
const print = std.debug.print;
pub fn solve(part: []u8, buffer: []u8, allocator: std.mem.Allocator) !void {
var lines = std.mem.splitScalar(u8, buffer, '\n');
var left = std.ArrayList(usize).init(allocator);
var right = std.ArrayList(usize).init(allocator);
defer left.deinit();
defer right.deinit();
if (std.mem.eql(u8, part, "1")) {
try part1(&lines, &left, &right, allocator);
} else {
try part2(&lines, &left, &right, allocator);
}
}
fn part1(lines: *std.mem.SplitIterator(u8, .scalar), left: *std.ArrayList(usize), right: *std.ArrayList(usize), allocator: std.mem.Allocator) !void {
while (lines.next()) |line| {
if (line.len > 0) {
var components = std.mem.split(u8, line, " ");
try left.append(try std.fmt.parseInt(usize, components.next().?, 10));
try right.append(try std.fmt.parseInt(usize, components.next().?, 10));
}
}
const left_s = try left.toOwnedSlice();
const right_s = try right.toOwnedSlice();
defer allocator.free(left_s);
defer allocator.free(right_s);
std.mem.sort(usize, left_s, {}, std.sort.asc(usize));
std.mem.sort(usize, right_s, {}, std.sort.asc(usize));
var sum: usize = 0;
for (left_s, right_s) |item_l, item_r| {
if (item_l > item_r) {
sum += item_l - item_r;
} else {
sum += item_r - item_l;
}
}
print("{d}\n", .{sum});
}
fn part2(lines: *std.mem.SplitIterator(u8, .scalar), left: *std.ArrayList(usize), right: *std.ArrayList(usize), allocator: std.mem.Allocator) !void {
while (lines.next()) |line| {
if (line.len > 0) {
var components = std.mem.split(u8, line, " ");
try left.append(try std.fmt.parseInt(usize, components.next().?, 10));
try right.append(try std.fmt.parseInt(usize, components.next().?, 10));
}
}
const left_s = try left.toOwnedSlice();
const right_s = try right.toOwnedSlice();
defer allocator.free(left_s);
defer allocator.free(right_s);
std.mem.sort(usize, right_s, {}, std.sort.asc(usize));
var map = std.AutoHashMap(usize, usize).init(allocator);
defer map.deinit();
var sum: usize = 0;
for (left_s) |item_l| {
sum += map.get(item_l) orelse blk: {
var amount: usize = 0;
for (right_s) |item_r| {
if (item_l == item_r) {
amount += item_l;
}
}
try map.put(item_l, amount);
break :blk amount;
};
}
print("{d}\n", .{sum});
}
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