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).

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];
}

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)) {
                std.debug.warn("Match: {}\n", i);
                count2 += 1;
            }
        }
    }

    std.debug.warn("       012345\n");

    std.debug.warn("Part 1: matches: {}\n", count1);
    std.debug.warn("Part 2: matches: {}\n", count2);
}