non brute force solution.

2020/day13/mainPart2.zig

@@ -1,7 +1,6 @@
 const input = @embedFile("inputPart2.txt");
 const std = @import("std");
 
-
 pub fn main() !void {
 
     //Data wrangling
@@ -9,10 +8,7 @@ pub fn main() !void {
     var busses: [68]u32 = std.mem.zeroes([68:0]u32);
     var i: u32 = 0;
 
-    while(it.next())
+    while (it.next()) |line| : (i += 1) {
-        |line|
-        :(i+=1)
-    {
         busses[i] = readNum(line);
     }
 
@@ -23,12 +19,8 @@ pub fn main() !void {
             busTotal += 1;
     }
 
-    const stepSize: u32 = 1;
+    var stepSize: u64 = 1;
     var n: u64 = 1;
-    var found: u8 = 0;
-
-    //Algorithm
-    while(found != busTotal):(n+=stepSize){
 
     for (busses, 0..) |bus, offset| {
         //skip
@@ -36,27 +28,15 @@ pub fn main() !void {
             continue;
         }
 
-            if(((n + offset) % bus) == 0){
+        while (((n + offset) % bus) != 0) : (n += stepSize) {}
-                found +=1;
-            }
-        }
 
-        if(found >= 7){
+        stepSize = stepSize * bus;
-            std.debug.print("tick {d} has {d} aligned!\n",.{n, found});
-        }
-
-        if(found == busTotal){
-            std.debug.print("Final tick {d}\n",.{n});
-            break;
-        }else{
-            found = 0;
-        }
     }
+    std.debug.print("tick: {d}", .{n});
 }
 
 fn readNum(line: []const u8) u32 {
     return std.fmt.parseInt(u32, line, 10) catch {
         return 0;
     };
-
 }