Add '2019/' from commit 'fc21396bc86bc0f706225f4f6e1d8294d344ca53'

git-subtree-dir: 2019
git-subtree-mainline: f1be11fca8
git-subtree-split: fc21396bc8

2019/04/src/main.zig

@@ -0,0 +1,53 @@
+const std = @import("std");
+
+const first = 171309;
+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).
+
+inline 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;
+
+    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];
+}
+
+inline 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 count1: i32 = 0;
+    var count2: i32 = 0;
+    var i: i32 = first;
+
+    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)) {
+                count2 += 1;
+            }
+        }
+    }
+
+    //std.debug.warn("       012345\n");
+
+    std.debug.warn("Part 1: matches: {}\n", count1);
+    std.debug.warn("Part 2: matches: {}\n", count2);
+}