From be0c611f0d140fd35199534b39a822b72208a1ee Mon Sep 17 00:00:00 2001
From: Nick Thomas <me@ur.gs>
Date: Wed, 4 Dec 2019 23:27:58 +0000
Subject: [PATCH] Day 4.2

---
 04/src/main.zig | 56 ++++++++++++++++++++++++++++++-------------------
 1 file changed, 34 insertions(+), 22 deletions(-)

diff --git a/04/src/main.zig b/04/src/main.zig
index c5310cf..b813914 100644
--- a/04/src/main.zig
+++ b/04/src/main.zig
@@ -1,42 +1,54 @@
 const std = @import("std");
 
 const first = 171309;
-const last  = 643603;
+const last = 643603;
 
 // - [x] It is a six-digit number (implied)
 // - [x] The value is within the range given in your puzzle input (implied)
 // - [x] Two adjacent digits are the same (like 22 in 122345).
 // - [x] Going from left to right, the digits never decrease; they only ever increase or stay the same (like 111123 or 135679).
 
-fn tests1(num: i32) anyerror!bool {
-    var buf: [6]u8 = undefined;
-    var numStr = try std.fmt.bufPrint(&buf, "{}", num);
+fn tests1(num: i32, str: []u8) bool {
+    if (str[0] > str[1] or str[1] > str[2] or
+        str[2] > str[3] or str[3] > str[4] or
+        str[4] > str[5]) return false;
 
-    if (numStr[0] > numStr[1] or
-        numStr[1] > numStr[2] or
-        numStr[2] > numStr[3] or
-        numStr[3] > numStr[4] or
-        numStr[4] > numStr[5]
-    ) return false;
+    return str[0] == str[1] or str[1] == str[2] or
+        str[2] == str[3] or str[3] == str[4] or
+        str[4] == str[5];
+}
 
-    return
-        numStr[0] == numStr[1] or
-        numStr[1] == numStr[2] or
-        numStr[2] == numStr[3] or
-        numStr[3] == numStr[4] or
-        numStr[4] == numStr[5];
+fn tests2(num: i32, str: []u8) bool {
+    if (str[0] == str[1] and str[1] != str[2]) return true; // [0 1]2 3 4 5
+    if (str[1] == str[2] and str[0] != str[1] and str[2] != str[3]) return true; //  0[1 2]3 4 5
+    if (str[2] == str[3] and str[1] != str[2] and str[3] != str[4]) return true; //  0 1[2 3]4 5
+    if (str[3] == str[4] and str[2] != str[3] and str[4] != str[5]) return true; //  0 1 2[3 4]5
+    if (str[4] == str[5] and str[3] != str[4]) return true; //  0 1 2 3[4 5]
+
+    return false;
 }
 
 pub fn main() anyerror!void {
-    var count: i32 = 0;
+    var count1: i32 = 0;
+    var count2: i32 = 0;
     var i: i32 = first;
 
-    while (i <= last) : (i+=1) {
-        if (try tests1(i)) {
-            //std.debug.warn("Match: {}\n", i);
-            count+=1;
+    while (i <= last) : (i += 1) {
+        var buf: [6]u8 = undefined;
+        var numStr = try std.fmt.bufPrint(&buf, "{}", i);
+
+        if (tests1(i, numStr)) {
+            count1 += 1;
+
+            if (tests2(i, numStr)) {
+                std.debug.warn("Match: {}\n", i);
+                count2 += 1;
+            }
         }
     }
 
-    std.debug.warn("Part 1: matches: {}\n", count);
+    std.debug.warn("       012345\n");
+
+    std.debug.warn("Part 1: matches: {}\n", count1);
+    std.debug.warn("Part 2: matches: {}\n", count2);
 }