solutions day1 and day2

1 files changed, 81 insertions, 0 deletions

diff --git a/src/day01.zig b/src/day01.zig
new file mode 100644
index 0000000..33b0a67
--- /dev/null
+++ b/src/day01.zig
@@ -0,0 +1,81 @@
+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, "part1")) {
+        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("Sum is {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("Sum is {d}\n", .{sum});
+}