Finish day06, part 2

src/days/day06.zig

@@ -18,7 +18,13 @@ pub fn run(allocator: std.mem.Allocator) !void {
 
     var operators_s: []const u8 = undefined;
 
+    var line_len: usize = 0;
     while (lines.next()) |line| {
+        if (line_len != 0) {
+            std.debug.assert(line_len == line.len);
+        }
+        line_len = line.len;
+
         std.debug.print("{s}\n", .{line});
         if (lines.peek() == null) {
             operators_s = line;
@@ -40,31 +46,54 @@ pub fn run(allocator: std.mem.Allocator) !void {
     defer allocator.free(results);
     @memset(results, 0);
 
-    for (numbers.items, 0..) |n, i| {
+    var oi: usize = operators.items.len - 1;
-        var numbers_i = std.mem.tokenizeScalar(u8, n, ' ');
+    var oni: usize = 0;
+    for (0..line_len) |i| {
+        const ri = line_len - 1 - i;
+
+        var number: u64 = 0;
+        var all_spaces = true;
+
+        var numbers_reverse_i = std.mem.reverseIterator(numbers.items);
         var ni: usize = 0;
-        while (numbers_i.next()) |number_s| {
+        while (numbers_reverse_i.next()) |n| {
-            defer ni += 1;
+            const c = n[ri];
+            if (c == ' ') {
+                continue;
+            } else {
+                defer ni += 1;
 
-            std.debug.print("number = {s}\n", .{number_s});
+                all_spaces = all_spaces and false;
+                const digit = try std.fmt.charToDigit(c, 10);
+                number += digit * std.math.pow(u64, 10, ni);
+            }
+        }
 
-            const number = try std.fmt.parseUnsigned(u64, number_s, 10);
+        if (all_spaces) {
-            const operator = operators.items[ni];
+            std.debug.print("all spaces\n", .{});
+            oi -= 1;
+            oni = 0;
+        } else {
+            defer oni += 1;
 
-            if (i == 0) {
+            const operator = operators.items[oi];
-                results[ni] = number;
+            std.debug.print("operator {d} = {c}\n", .{oi, operator});
+
+            std.debug.print("oni = {d}\n", .{oni});
+
+            if (oni == 0) {
+                results[oi] = number;
             } else {
                 if (operator == '+') {
-                    results[ni] += number;
+                    results[oi] += number;
                 } else if (operator == '*') {
-                    results[ni] *= number;
+                    results[oi] *= number;
                 } else {
-                    std.debug.print("operator = {c}\n", .{operator});
                     unreachable;
                 }
             }
 
-            std.debug.print("result = {d}\n", .{results[ni]});
+            std.debug.print("result = {d}\n", .{results[oi]});
         }
     }