refactor: clean up repository layout

1 files changed, 233 insertions, 0 deletions

diff --git a/2025/day11.asm b/2025/day11.asm
new file mode 100644
index 0000000..c3cd930
--- /dev/null
+++ b/2025/day11.asm
@@ -0,0 +1,233 @@
+; Advent of Code 2025 - Day 11
+
+bits 64
+default rel
+
+global _start
+
+%include "utils/io.asm"
+
+%define RAW_SIZE   262144
+%define NCODES     17576        ; 26^3 possible 3-letter names
+%define OUT_CODE   10003        ; encode("out")
+%define YOU_CODE   16608        ; encode("you")
+%define SVR_CODE   12731        ; encode("svr")
+%define DAC_CODE   2030         ; encode("dac")
+%define FFT_CODE   3529         ; encode("fft")
+%define MAXEDGES   8192
+
+section .data
+    input_path db "input/day11.txt", 0
+
+    label1     db "Part 1: ", 0
+    label2     db "Part 2: ", 0
+
+section .bss
+    raw           resb RAW_SIZE
+    adj_head      resq NCODES    ; first child index in `child`
+    adj_cnt       resq NCODES    ; number of children
+    child         resq MAXEDGES  ; flat child codes
+    memo          resq NCODES    ; path counts, -1 = not computed
+    blocked       resb NCODES    ; 1 = treat node as a dead end
+
+    raw_len       resq 1
+    t1            resq 1
+    t2            resq 1
+
+section .text
+
+_start:
+    mov     rdi, input_path
+    lea     rsi, [raw]
+    mov     rdx, RAW_SIZE
+    call    read_file
+    mov     [raw_len], rax
+
+    ; memo = -1 everywhere
+    mov     rax, -1
+    lea     rdi, [memo]
+    mov     rcx, NCODES
+    rep     stosq
+
+    ; parse "name: a b c" adjacency lines
+    lea     rsi, [raw]
+    mov     rax, [raw_len]
+    lea     r13, [raw + rax]   ; end pointer
+    xor     r12, r12           ; child write index
+parse_line:
+    cmp     rsi, r13
+    jae     parse_done
+    mov     al, [rsi]
+    cmp     al, 10
+    je      parse_skip
+    cmp     al, 13
+    je      parse_skip
+    call    encode3            ; RAX = node code
+    mov     r10, rax
+    mov     [adj_head + r10*8], r12
+skip_sep:
+    mov     al, [rsi]
+    cmp     al, ':'
+    je      .adv
+    cmp     al, ' '
+    je      .adv
+    jmp     children
+.adv:
+    inc     rsi
+    jmp     skip_sep
+children:
+    xor     r11, r11           ; child count
+child_loop:
+    cmp     rsi, r13
+    jae     child_done
+    mov     al, [rsi]
+    cmp     al, 10
+    je      child_done
+    cmp     al, 13
+    je      child_done
+    cmp     al, ' '
+    je      child_space
+    call    encode3
+    mov     [child + r12*8], rax
+    inc     r12
+    inc     r11
+    jmp     child_loop
+child_space:
+    inc     rsi
+    jmp     child_loop
+child_done:
+    mov     [adj_cnt + r10*8], r11
+skip_eol:
+    cmp     rsi, r13
+    jae     parse_done
+    mov     al, [rsi]
+    inc     rsi
+    cmp     al, 10
+    jne     skip_eol
+    jmp     parse_line
+parse_skip:
+    inc     rsi
+    jmp     parse_line
+parse_done:
+
+    ; part 1: paths you -> out
+    call    clear_memo
+    mov     rdi, YOU_CODE
+    call    count
+    mov     [t1], rax
+
+    ; part 2: paths svr -> out visiting both dac and fft, via inclusion-exclusion
+    call    clear_memo
+    mov     rdi, SVR_CODE
+    call    count
+    mov     r12, rax                   ; N(all)
+
+    mov     byte [blocked + DAC_CODE], 1
+    call    clear_memo
+    mov     rdi, SVR_CODE
+    call    count
+    mov     r13, rax                   ; N(avoid dac)
+    mov     byte [blocked + DAC_CODE], 0
+
+    mov     byte [blocked + FFT_CODE], 1
+    call    clear_memo
+    mov     rdi, SVR_CODE
+    call    count
+    mov     r14, rax                   ; N(avoid fft)
+    mov     byte [blocked + FFT_CODE], 0
+
+    mov     byte [blocked + DAC_CODE], 1
+    mov     byte [blocked + FFT_CODE], 1
+    call    clear_memo
+    mov     rdi, SVR_CODE
+    call    count                      ; N(avoid both) in rax
+    mov     byte [blocked + DAC_CODE], 0
+    mov     byte [blocked + FFT_CODE], 0
+
+    sub     r12, r13
+    sub     r12, r14
+    add     r12, rax
+    mov     [t2], r12
+
+    mov     rcx, label1
+    call    print_string
+    mov     rax, [t1]
+    call    print_int64
+    call    print_newline
+
+    mov     rcx, label2
+    call    print_string
+    mov     rax, [t2]
+    call    print_int64
+    call    print_newline
+
+    mov     rax, SYS_EXIT
+    xor     rdi, rdi
+    syscall
+
+; clear_memo: reset all memo entries to -1. Clobbers RAX, RCX, RDI.
+clear_memo:
+    mov     rax, -1
+    lea     rdi, [memo]
+    mov     rcx, NCODES
+    rep     stosq
+    ret
+
+; encode3: read 3 lowercase letters at [RSI] into a base-26 code, advance RSI.
+;   Output: RAX = code. Clobbers RAX, RDX.
+encode3:
+    movzx   eax, byte [rsi]
+    sub     eax, 'a'
+    imul    eax, eax, 676
+    movzx   edx, byte [rsi + 1]
+    sub     edx, 'a'
+    imul    edx, edx, 26
+    add     eax, edx
+    movzx   edx, byte [rsi + 2]
+    sub     edx, 'a'
+    add     eax, edx
+    add     rsi, 3
+    ret
+
+; count: number of paths from node RDI to out. Memoised DFS over the DAG.
+;   Output: RAX. Clobbers RAX; preserves everything else via the stack.
+count:
+    cmp     rdi, OUT_CODE
+    je      .one
+    cmp     byte [blocked + rdi], 0
+    jne     .zero
+    mov     rax, [memo + rdi*8]
+    cmp     rax, -1
+    jne     .ret
+    push    r12
+    push    r13
+    push    r14
+    push    r15
+    mov     r12, rdi
+    mov     r13, [adj_head + r12*8]
+    mov     r14, r13
+    add     r14, [adj_cnt + r12*8]
+    xor     r15, r15
+.loop:
+    cmp     r13, r14
+    jge     .done
+    mov     rdi, [child + r13*8]
+    call    count
+    add     r15, rax
+    inc     r13
+    jmp     .loop
+.done:
+    mov     [memo + r12*8], r15
+    mov     rax, r15
+    pop     r15
+    pop     r14
+    pop     r13
+    pop     r12
+    ret
+.one:
+    mov     rax, 1
+    ret
+.zero:
+    xor     eax, eax
+.ret:
+    ret