add linked list exercise

config.json

@@ -369,6 +369,19 @@
           "loops",
           "strings"
         ]
+      },
+      {
+        "slug": "linked-list",
+        "name": "Linked List",
+        "uuid": "b79e66ed-54b3-43da-a4ce-884d81447ce5",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 4,
+        "topics": [
+          "functions",
+          "pointers",
+          "structs"
+        ]
       }
     ]
   },
@@ -423,4 +436,4 @@
     "runtime/standalone_executable",
     "used_for/embedded_systems"
   ]
-}
+}

exercises/practice/linked-list/.docs/instructions.md

@@ -0,0 +1,28 @@
+# Instructions
+
+Implement a doubly linked list.
+
+Like an array, a linked list is a simple linear data structure. Several
+common data types can be implemented using linked lists, like queues,
+stacks, and associative arrays.
+
+A linked list is a collection of data elements called *nodes*. In a
+*singly linked list* each node holds a value and a link to the next node.
+In a *doubly linked list* each node also holds a link to the previous
+node.
+
+You will write an implementation of a doubly linked list. Implement a
+Node to hold a value and pointers to the next and previous nodes. Then
+implement a List which holds references to the first and last node and
+offers an array-like interface for adding and removing items:
+
+* `push` (*insert value at back*);
+* `pop` (*remove value at back*);
+* `shift` (*remove value at front*).
+* `unshift` (*insert value at front*);
+
+To keep your implementation simple, the tests will not cover error
+conditions. Specifically: `pop` or `shift` will never be called on an
+empty list.
+
+If you want to know more about linked lists, check [Wikipedia](https://en.wikipedia.org/wiki/Linked_list).

exercises/practice/linked-list/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "blurb": "Implement a doubly linked list",
+  "authors": [
+    "sudhackar"
+  ],
+  "contributors": [],
+  "files": {
+    "solution": [
+      "linked_list.asm"
+    ],
+    "test": [
+      "linked_list_test.c"
+    ],
+    "example": [
+      ".meta/example.asm"
+    ]
+  },
+  "source": "Classic computer science topic"
+}

exercises/practice/linked-list/.meta/example.asm

@@ -0,0 +1,221 @@
+default rel
+; a Node in the doubly linked-list
+struc Node
+        ; pointer to previous node
+        .Prev:  resq    1
+        ; pointer to next node
+        .Next:  resq    1
+        ; int data
+        .Data:  resd    1
+endstruc
+
+; references to start and end of a list
+struc List
+        ; pointer to First node in the List
+        .First  resq    1
+        ; pointer to Last node in the list
+        .Last   resq    1
+endstruc
+
+section .bss
+; store the single instance of List to store pointers to First and Last nodes
+list:
+        resb List_size
+; space for 16 nodes which will be "allocated" sequentially
+nodes:
+        resb 0x10*Node_size
+; an integer that has the next available node from nodes to "allocate"
+currnodeidx:
+        resq 1
+
+section .text
+
+global list_create
+global list_count
+global list_push
+global list_pop
+global list_unshift
+global list_shift
+global list_delete
+global list_destroy
+
+get_list:
+        ; reset current node index to 0
+        mov     dword [currnodeidx], 0
+        ; return pointer to list
+        lea     rax, [list]
+        ret
+get_node:
+        movsx   rax, dword [currnodeidx]
+        lea     edx, [rax+1]
+        imul    rax, rax, Node_size
+        mov     dword [currnodeidx], edx
+        lea     rdx, [nodes]
+        add     rax, rdx
+        ret
+
+list_node_create:
+        mov     ecx, edx
+        call    get_node
+        test    rax, rax
+        je      .err
+        mov     qword [rax+Node.Prev], rdi
+        mov     qword [rax+Node.Next], rsi
+        mov     dword [rax+Node.Data], ecx
+.err:
+        ret
+list_create:
+        call    get_list
+        test    rax, rax
+        je      .err
+        mov     qword [rax+List.First], 0
+        mov     qword [rax+List.Last], 0
+.err:
+        ret
+list_count:
+        lea     rax, [list]
+        test    rax, rax
+        je      .fin_loop_count
+        mov     rdi, rax
+        mov     rdx, qword [rdi+List.First]
+        xor     eax, eax
+.loop_count:
+        test    rdx, rdx
+        je      .fin_loop_count
+        mov     rdx, qword [rdx+Node.Next]
+        inc     rax
+        jmp     .loop_count
+.fin_loop_count:
+        ret
+list_push:
+        lea     rax, [list]
+        test    rax, rax
+        je      .err
+        mov     r8, rax
+        mov     edx, edi
+        mov     rdi, qword [r8+List.Last]
+        xor     esi, esi
+        call    list_node_create
+        test    rax, rax
+        je      .err
+        cmp     qword [r8+List.First], 0
+        mov     qword [r8+List.Last], rax
+        jne     .first_set
+        mov     qword [r8+List.First], rax
+        ret
+.first_set:
+        mov     rdx, qword [rax+Node.Prev]
+        mov     qword [rdx+Node.Next], rax
+.err:
+        ret
+list_pop:
+        lea     rdi, [list]
+        mov     rax, qword [rdi+List.Last]
+        mov     rdx, qword [rax+Node.Prev]
+        mov     r8d, dword [rax+Node.Data]
+        mov     qword [rdi+List.Last], rdx
+        cmp     qword [rdi+List.First], rax
+        jne     .set_prev_next
+        mov     qword [rdi+List.First], 0
+        jmp     .empty
+.set_prev_next:
+        mov     qword [rdx+Node.Next], 0
+.empty:
+        mov     qword [rax+Node.Prev], 0
+        mov     qword [rax+Node.Next], 0
+        mov     dword [rax+Node.Data], 0
+        mov     eax, r8d
+        ret
+list_unshift:
+        mov     edx, edi
+        lea     rdi, [list]
+        mov     rsi, qword [rdi+List.First]
+        mov     r8, rdi
+        xor     edi, edi
+        call    list_node_create
+        test    rax, rax
+        je      .err
+        cmp     qword [r8+List.Last], 0
+        mov     qword [r8+List.First], rax
+        jne     .set_next_prev
+        mov     qword [r8+List.Last], rax
+        ret
+.set_next_prev:
+        mov     rdx, qword [rax+Node.Next]
+        mov     qword [rdx+Node.Prev], rax
+.err:
+        ret
+list_shift:
+        lea     rdi, [list]
+        mov     rax, qword [rdi+List.First]
+        mov     rdx, qword [rax+Node.Next]
+        mov     r8d, dword [rax+Node.Data]
+        mov     qword [rdi+List.First], rdx
+        cmp     qword [rdi+List.Last], rax
+        jne     .set_next_prev
+        mov     qword [rdi+List.Last], 0
+        jmp     .zero
+.set_next_prev:
+        mov     qword [rdx+Node.Prev], 0
+.zero:
+        mov     qword [rax+Node.Prev], 0
+        mov     qword [rax+Node.Next], 0
+        mov     dword [rax+Node.Data], 0
+        mov     eax, r8d
+        ret
+list_delete:
+        mov     esi, edi
+        lea     rdi, [list]
+        mov     r8, qword [rdi+List.First]
+        mov     rax, r8
+.search_loop:
+        test    rax, rax
+        je      .err
+        mov     rdx, qword [rax+Node.Next]
+        cmp     dword [rax+Node.Data], esi
+        jne     .Next
+        mov     rcx, qword [rax+Node.Prev]
+        cmp     rax, r8
+        jne     .set_prev_next
+        mov     qword [rdi+List.First], rdx
+        jmp     .last_compare
+.set_prev_next:
+        mov     qword [rcx+Node.Next], rdx
+.last_compare:
+        cmp     qword [rdi+List.Last], rax
+        jne     .set_next_prev
+        mov     qword [rdi+List.Last], rcx
+        jmp     .zero
+.set_next_prev:
+        mov     rdx, qword [rax+Node.Next]
+        mov     qword [rdx+Node.Prev], rcx
+.zero:
+        mov     qword [rax+Node.Prev], 0
+        mov     qword [rax+Node.Next], 0
+        mov     dword [rax+Node.Data], 0
+        ret
+.Next:
+        mov     rax, rdx
+        jmp     .search_loop
+.err:
+        ret
+list_destroy:
+        call    get_list
+        test    rax, rax
+        je      .err
+        mov     rdi, rax
+        mov     rax, qword [rdi+List.First]
+.loop:
+        test    rax, rax
+        je      .zero
+        mov     rdx, qword [rax+Node.Next]
+        mov     qword [rax+Node.Prev], 0
+        mov     qword [rax+Node.Next], 0
+        mov     dword [rax+Node.Data], 0
+        mov     rax, rdx
+        jmp     .loop
+.zero:
+        mov     qword [rdi+List.First], 0
+        mov     qword [rdi+List.Last], 0
+.err:
+        ret

exercises/practice/linked-list/.meta/tests.toml

@@ -0,0 +1,60 @@
+# This is an auto-generated file. Regular comments will be removed when this
+# file is regenerated. Regenerating will not touch any manually added keys,
+# so comments can be added in a "comment" key.
+
+[7f7e3987-b954-41b8-8084-99beca08752c]
+description = "pop gets element from the list"
+
+[c3f67e5d-cfa2-4c3e-a18f-7ce999c3c885]
+description = "push/pop respectively add/remove at the end of the list"
+
+[00ea24ce-4f5c-4432-abb4-cc6e85462657]
+description = "shift gets an element from the list"
+
+[37962ee0-3324-4a29-b588-5a4c861e6564]
+description = "shift gets first element from the list"
+
+[30a3586b-e9dc-43fb-9a73-2770cec2c718]
+description = "unshift adds element at start of the list"
+
+[042f71e4-a8a7-4cf0-8953-7e4f3a21c42d]
+description = "pop, push, shift, and unshift can be used in any order"
+
+[88f65c0c-4532-4093-8295-2384fb2f37df]
+description = "count an empty list"
+
+[fc055689-5cbe-4cd9-b994-02e2abbb40a5]
+description = "count a list with items"
+
+[8272cef5-130d-40ea-b7f6-5ffd0790d650]
+description = "count is correct after mutation"
+
+[229b8f7a-bd8a-4798-b64f-0dc0bb356d95]
+description = "popping to empty doesn't break the list"
+
+[4e1948b4-514e-424b-a3cf-a1ebbfa2d1ad]
+description = "shifting to empty doesn't break the list"
+
+[e8f7c600-d597-4f79-949d-8ad8bae895a6]
+description = "deletes the only element"
+
+[fd65e422-51f3-45c0-9fd0-c33da638f89b]
+description = "deletes the element with the specified value from the list"
+
+[59db191a-b17f-4ab7-9c5c-60711ec1d013]
+description = "deletes the element with the specified value from the list, re-assigns tail"
+
+[58242222-5d39-415b-951d-8128247f8993]
+description = "deletes the element with the specified value from the list, re-assigns head"
+
+[ee3729ee-3405-4bd2-9bad-de0d4aa5d647]
+description = "deletes the first of two elements"
+
+[47e3b3b4-b82c-4c23-8c1a-ceb9b17cb9fb]
+description = "deletes the second of two elements"
+
+[7b420958-f285-4922-b8f9-10d9dcab5179]
+description = "delete does not modify the list if the element is not found"
+
+[7e04828f-6082-44e3-a059-201c63252a76]
+description = "deletes only the first occurrence"