Day 3HEADmain

1 files changed, 52 insertions, 0 deletions

diff --git a/src/days/3/3.zig b/src/days/3/3.zig
new file mode 100644
index 0000000..66c6f9c
--- /dev/null
+++ b/src/days/3/3.zig
@@ -0,0 +1,52 @@
+const std = @import("std");
+
+pub fn main() !void {
+
+    const buf = @embedFile("input");
+
+    var lines = std.mem.tokenizeScalar(u8, buf, '\n');
+
+    var sum: u64 = 0;
+
+    const n = 12; // n = 2 for p1
+
+    var digits_ind: [n]?usize = undefined;
+
+    while (lines.next()) |line| {
+
+        digits_ind[0] = 0;
+        for (1..n) |i| {
+            digits_ind[i] = null;
+        }
+
+        outer: for (1..line.len) |i| {
+
+            const c = line[i];
+
+            for (0..@min(n, i)) |digit| {
+
+                const index = digits_ind[digit] orelse line.len;
+                const char = if (index < line.len) line[index] else 0;
+
+                if ((c > char and i < line.len-(n-1-digit)) or char == 0) {
+                    digits_ind[digit] = i;
+
+                    for (digit+1..n) |j| {
+                        digits_ind[j] = null;
+                    }
+                    continue :outer;
+                }
+            }
+        }
+
+        var num: u64 = 0;
+        for (digits_ind, 0..) |ind, i| {
+            num += (line[ind.?] - '0')*std.math.pow(u64, 10, n-i-1);
+        }
+
+
+        sum += num;
+    }
+
+    std.debug.print("{}\n", .{sum});
+}