From 4959a34dcb6f4364fb4fa2e97f2b03f3cd3fd72c Mon Sep 17 00:00:00 2001
From: Sijmen Schoon <me@sijmenschoon.nl>
Date: Wed, 9 Dec 2020 16:17:02 +0100
Subject: [PATCH] Add c64 day 1 part 2

---
 c64/day01.asm | 123 +++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 101 insertions(+), 22 deletions(-)

diff --git a/c64/day01.asm b/c64/day01.asm
index 7b01f33..284a63b 100644
--- a/c64/day01.asm
+++ b/c64/day01.asm
@@ -29,6 +29,9 @@ day01:
     move_16_imm(input_pointer, day01_input)
     ldy #0
 
+    lda #0
+    sta zp_temp
+
 !line:
     // Create a temporary 16-bit integer to store the result in
     // in between digits.
@@ -73,9 +76,9 @@ day01:
     lda (input_pointer), y
     bne !line-
 
-    move_16_imm($03, str_parse_done)
-    jsr write_string
-
+    //
+    // Part 1
+    //
     ldy #0
     !loop:
         // Subtract the number from 2020 to find the needed value.
@@ -102,9 +105,6 @@ day01:
     sec
     jsr multiply_16bit_unsigned
 
-    move_16_imm($03, str_calc_done)
-    jsr write_string
-
     // Print the 32-bit result as decimal.
     lda $25
     sta udivmod32_dividend + 3
@@ -116,27 +116,106 @@ day01:
     sta udivmod32_dividend + 0
     jsr print_decimal_u32
 
-    rts
-
-!error:
-    move_16_imm($03, str_no_result)
+    move_16_imm($03, str_part2)
     jsr write_string
+
+.const val_a = $26
+.const val_b = $fd
+.const val_c = $44
+.const val_temp = $46
+.const outer_i = $1f
+
+    //
+    // Part 2
+    //
+    ldx #0
+    !outer_loop:
+        ldy #0
+        lda tree_values_lo, x
+        sta val_a + 0
+        lda tree_values_hi, x
+        sta val_a + 1
+        stx outer_i
+
+        !inner_loop:
+            // Subtract the numbers from 2020 to find the needed value.
+            lda tree_values_lo, y
+            sta val_b + 0
+            bne !not_zero+
+
+            lda tree_values_hi, y
+            bne !not_zero+
+                ldx outer_i
+                inx
+                bne !outer_loop-
+            !not_zero:
+
+            lda tree_values_hi, y
+            sta val_b + 1
+
+            lda val_a + 0
+            clc
+            adc val_b + 0
+            sta val_temp + 0
+
+            lda val_a + 1
+            adc val_b + 1
+            sta val_temp + 1
+
+            lda val_temp + 0
+            eor #$ff
+            sec
+            adc #<2020
+            sta $03
+            sta val_c + 0
+
+            lda val_temp + 1
+            eor #$ff
+            adc #>2020
+            sta $04
+            sta val_c + 1
+
+            iny
+            jsr tree_contains
+            bne !inner_loop-
+
+    // Multiply the three numbers together
+    sec
+    jsr multiply_16bit_unsigned
+
+    u16_u16_move($30, $22)
+    u16_u16_move($32, $24)
+
+    u16_u16_move($34, val_c)
+    move_16_imm($36, 0)
+
+    jsr multiply_32bit_unsigned
+
+    // Print the 32-bit result as decimal.
+    u16_u16_move(udivmod32_dividend, $38)
+    u16_u16_move(udivmod32_dividend + 2, $3a)
+    u16_u16_move(udivmod32_dividend + 4, $3c)
+    u16_u16_move(udivmod32_dividend + 6, $3e)
+    jsr print_decimal_u32
+
+    move_16_imm($03, str_done)
+    jsr write_string
+
     rts
 
 
 str_title:
-    .text "# Day 01, part 1:"
-    .byte '\n', 0
+    .text "# Day 01"
+    .byte '\n', '\n'
+    .text "Part 1: "
+    .byte 0
 
-str_parse_done:
-    .text "* Finished parsing"
-    .byte '\n', 0
-
-str_calc_done:
-    .text "* Finished calculating"
-    .byte '\n', 0
-
-str_no_result:
+str_part2:
     .byte '\n'
-    .text "! Could not find a result"
+    .text "Part 2: "
+    .byte 0
+
+str_done:
+    .byte '\n', '\n'
+    .text "* Done"
     .byte '\n', 0