From d7f142d70dfb77afcf2219a63490727b7671429f Mon Sep 17 00:00:00 2001
From: keiravillekode <keiravillekode@gmail.com>
Date: Fri, 9 Aug 2024 22:11:30 +1000
Subject: [PATCH] Add pascals-triangle (#276)

---
 config.json                                   |   8 +
 .../practice/pascals-triangle/.docs/hints.md  |   6 +
 .../.docs/instructions.append.md              |  10 +
 .../pascals-triangle/.docs/instructions.md    |  35 +++
 .../pascals-triangle/.docs/introduction.md    |  22 ++
 .../pascals-triangle/.meta/config.json        |  19 ++
 .../pascals-triangle/.meta/example.mips       |  50 ++++
 .../pascals-triangle/.meta/tests.toml         |  34 +++
 exercises/practice/pascals-triangle/impl.mips |  11 +
 .../practice/pascals-triangle/runner.mips     | 225 ++++++++++++++++++
 10 files changed, 420 insertions(+)
 create mode 100644 exercises/practice/pascals-triangle/.docs/hints.md
 create mode 100644 exercises/practice/pascals-triangle/.docs/instructions.append.md
 create mode 100644 exercises/practice/pascals-triangle/.docs/instructions.md
 create mode 100644 exercises/practice/pascals-triangle/.docs/introduction.md
 create mode 100644 exercises/practice/pascals-triangle/.meta/config.json
 create mode 100644 exercises/practice/pascals-triangle/.meta/example.mips
 create mode 100644 exercises/practice/pascals-triangle/.meta/tests.toml
 create mode 100644 exercises/practice/pascals-triangle/impl.mips
 create mode 100644 exercises/practice/pascals-triangle/runner.mips

diff --git a/config.json b/config.json
index 2d8a100..0768288 100644
--- a/config.json
+++ b/config.json
@@ -500,6 +500,14 @@
         "prerequisites": [],
         "difficulty": 4
       },
+      {
+        "slug": "pascals-triangle",
+        "name": "Pascal's Triangle",
+        "uuid": "4bf78b97-f958-4327-bdbb-f36dcd6c7f15",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 6
+      },
       {
         "slug": "pig-latin",
         "name": "Pig Latin",
diff --git a/exercises/practice/pascals-triangle/.docs/hints.md b/exercises/practice/pascals-triangle/.docs/hints.md
new file mode 100644
index 0000000..52d65b0
--- /dev/null
+++ b/exercises/practice/pascals-triangle/.docs/hints.md
@@ -0,0 +1,6 @@
+# Hints
+
+## General
+
+- The `$t0-9` registers can be used to temporarily store values
+- The instructions specify which registers are used as input and output
diff --git a/exercises/practice/pascals-triangle/.docs/instructions.append.md b/exercises/practice/pascals-triangle/.docs/instructions.append.md
new file mode 100644
index 0000000..812c18a
--- /dev/null
+++ b/exercises/practice/pascals-triangle/.docs/instructions.append.md
@@ -0,0 +1,10 @@
+# Instructions append
+
+## Registers
+
+| Register | Usage        | Type    | Description             |
+| -------- | ------------ | ------- | ----------------------- |
+| `$a0`    | input        | integer | number of triangle rows |
+| `$a1`    | input/output | address | array of words          |
+| `$v0`    | output       | integer | number of output words  |
+| `$t0-9`  | temporary    | any     | for temporary storage   |
diff --git a/exercises/practice/pascals-triangle/.docs/instructions.md b/exercises/practice/pascals-triangle/.docs/instructions.md
new file mode 100644
index 0000000..0f58f00
--- /dev/null
+++ b/exercises/practice/pascals-triangle/.docs/instructions.md
@@ -0,0 +1,35 @@
+# Instructions
+
+Your task is to output the first N rows of Pascal's triangle.
+
+[Pascal's triangle][wikipedia] is a triangular array of positive integers.
+
+In Pascal's triangle, the number of values in a row is equal to its row number (which starts at one).
+Therefore, the first row has one value, the second row has two values, and so on.
+
+The first (topmost) row has a single value: `1`.
+Subsequent rows' values are computed by adding the numbers directly to the right and left of the current position in the previous row.
+
+If the previous row does _not_ have a value to the left or right of the current position (which only happens for the leftmost and rightmost positions), treat that position's value as zero (effectively "ignoring" it in the summation).
+
+## Example
+
+Let's look at the first 5 rows of Pascal's Triangle:
+
+```text
+    1
+   1 1
+  1 2 1
+ 1 3 3 1
+1 4 6 4 1
+```
+
+The topmost row has one value, which is `1`.
+
+The leftmost and rightmost values have only one preceding position to consider, which is the position to its right respectively to its left.
+With the topmost value being `1`, it follows from this that all the leftmost and rightmost values are also `1`.
+
+The other values all have two positions to consider.
+For example, the fifth row's (`1 4 6 4 1`) middle value is `6`, as the values to its left and right in the preceding row are `3` and `3`:
+
+[wikipedia]: https://en.wikipedia.org/wiki/Pascal%27s_triangle
diff --git a/exercises/practice/pascals-triangle/.docs/introduction.md b/exercises/practice/pascals-triangle/.docs/introduction.md
new file mode 100644
index 0000000..60b8ec3
--- /dev/null
+++ b/exercises/practice/pascals-triangle/.docs/introduction.md
@@ -0,0 +1,22 @@
+# Introduction
+
+With the weather being great, you're not looking forward to spending an hour in a classroom.
+Annoyed, you enter the class room, where you notice a strangely satisfying triangle shape on the blackboard.
+Whilst waiting for your math teacher to arrive, you can't help but notice some patterns in the triangle: the outer values are all ones, each subsequent row has one more value than its previous row and the triangle is symmetrical.
+Weird!
+
+Not long after you sit down, your teacher enters the room and explains that this triangle is the famous [Pascal's triangle][wikipedia].
+
+Over the next hour, your teacher reveals some amazing things hidden in this triangle:
+
+- It can be used to compute how many ways you can pick K elements from N values.
+- It contains the Fibonacci sequence.
+- If you color odd and even numbers differently, you get a beautiful pattern called the [Sierpiński triangle][wikipedia-sierpinski-triangle].
+
+The teacher implores you and your classmates to lookup other uses, and assures you that there are lots more!
+At that moment, the school bell rings.
+You realize that for the past hour, you were completely absorbed in learning about Pascal's triangle.
+You quickly grab your laptop from your bag and go outside, ready to enjoy both the sunshine _and_ the wonders of Pascal's triangle.
+
+[wikipedia]: https://en.wikipedia.org/wiki/Pascal%27s_triangle
+[wikipedia-sierpinski-triangle]: https://en.wikipedia.org/wiki/Sierpi%C5%84ski_triangle
diff --git a/exercises/practice/pascals-triangle/.meta/config.json b/exercises/practice/pascals-triangle/.meta/config.json
new file mode 100644
index 0000000..3de2449
--- /dev/null
+++ b/exercises/practice/pascals-triangle/.meta/config.json
@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "impl.mips"
+    ],
+    "test": [
+      "runner.mips"
+    ],
+    "example": [
+      ".meta/example.mips"
+    ]
+  },
+  "blurb": "Compute Pascal's triangle up to a given number of rows.",
+  "source": "Pascal's Triangle at Wolfram Math World",
+  "source_url": "https://www.wolframalpha.com/input/?i=Pascal%27s+triangle"
+}
diff --git a/exercises/practice/pascals-triangle/.meta/example.mips b/exercises/practice/pascals-triangle/.meta/example.mips
new file mode 100644
index 0000000..a6fa889
--- /dev/null
+++ b/exercises/practice/pascals-triangle/.meta/example.mips
@@ -0,0 +1,50 @@
+# | Register | Usage        | Type    | Description                      |
+# | -------- | ------------ | ------- | -------------------------------- |
+# | `$a0`    | input        | integer | number of triangle rows          |
+# | `$a1`    | input/output | address | start of array of words          |
+# | `$v0`    | output       | integer | number of output words           |
+# | `$t0`    | temporary    | address | output pointer                   |
+# | `$t1`    | temporary    | integer | number of bytes in $a0 words     |
+# | `$t2`    | temporary    | integer | row length, in bytes             |
+# | `$t3`    | temporary    | address | pointer into previous row        |
+# | `$t4`    | temporary    | address | initial 1 of current row         |
+# | `$t5`    | temporary    | address | final 1 of current row           |
+# | `$t6`    | temporary    | integer | left value from previous row     |
+# | `$t7`    | temporary    | integer | right value from previous row    |
+# | `$t8`    | temporary    | integer | sum two values from previous row |
+
+.globl rows
+
+rows:
+        move    $t0, $a1                # output pointer
+        beqz    $a0, done               # stop immediately if 0 rows
+        sll     $t1, $a0, 2             # number of bytes in $a0 words
+        move    $t2, $zero              # row length, in bytes
+        li      $t7, 1                  # value for first row
+
+next_row:
+        move   $t4, $t0                 # address of initial 1 of current row
+        add    $t5, $t0, $t2            # address of final 1 of current row
+        addi   $t2, $t2, 4              # row length, in bytes
+        move   $t6, $zero               # left value from previous row
+        beq    $t0, $t5, last_column
+
+next_column:
+        lw     $t7, 0($t3)              # read from previous row
+        addi   $t3, $t3, 4
+        add    $t8, $t6, $t7            # sum two values from previous row
+        move   $t6, $t7
+        sw     $t8, 0($t0)              # write output
+        addi   $t0, $t0, 4
+        bne    $t0, $t5, next_column
+
+last_column:
+        sw     $t7, 0($t0)              # write output
+        addi   $t0, $t0, 4
+        move   $t3, $t4                 # start of most recent row
+        bne    $t2, $t1, next_row       # repeat until we have final row length
+
+done:
+        sub    $v0, $t0, $a1            # subtract start of output
+        srl    $v0, $v0, 2              # convert to number of words
+        jr     $ra
diff --git a/exercises/practice/pascals-triangle/.meta/tests.toml b/exercises/practice/pascals-triangle/.meta/tests.toml
new file mode 100644
index 0000000..2db0ee5
--- /dev/null
+++ b/exercises/practice/pascals-triangle/.meta/tests.toml
@@ -0,0 +1,34 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[9920ce55-9629-46d5-85d6-4201f4a4234d]
+description = "zero rows"
+
+[70d643ce-a46d-4e93-af58-12d88dd01f21]
+description = "single row"
+
+[a6e5a2a2-fc9a-4b47-9f4f-ed9ad9fbe4bd]
+description = "two rows"
+
+[97206a99-79ba-4b04-b1c5-3c0fa1e16925]
+description = "three rows"
+
+[565a0431-c797-417c-a2c8-2935e01ce306]
+description = "four rows"
+
+[06f9ea50-9f51-4eb2-b9a9-c00975686c27]
+description = "five rows"
+
+[c3912965-ddb4-46a9-848e-3363e6b00b13]
+description = "six rows"
+
+[6cb26c66-7b57-4161-962c-81ec8c99f16b]
+description = "ten rows"
diff --git a/exercises/practice/pascals-triangle/impl.mips b/exercises/practice/pascals-triangle/impl.mips
new file mode 100644
index 0000000..d94eca2
--- /dev/null
+++ b/exercises/practice/pascals-triangle/impl.mips
@@ -0,0 +1,11 @@
+# | Register | Usage        | Type    | Description             |
+# | -------- | ------------ | ------- | ----------------------- |
+# | `$a0`    | input        | integer | number of triangle rows |
+# | `$a1`    | input/output | address | array of words          |
+# | `$v0`    | output       | integer | number of output words  |
+# | `$t0-9`  | temporary    | any     | for temporary storage   |
+
+.globl rows
+
+rows:
+        jr $ra
diff --git a/exercises/practice/pascals-triangle/runner.mips b/exercises/practice/pascals-triangle/runner.mips
new file mode 100644
index 0000000..8092716
--- /dev/null
+++ b/exercises/practice/pascals-triangle/runner.mips
@@ -0,0 +1,225 @@
+#
+# Test rows with some examples
+#
+# a0 - input number, for callee
+# a1 - pointer to output array of entries, for callee
+# s0 - num of tests left to run
+# s1 - address of input number
+# s2 - address of expected entries
+# s3 - address of expected number of entries
+# s4 - copy of output location
+# t0 - address of expected entry
+# t1 - expected entry
+# t2 - address of actual entry
+# t3 - actual entry
+# t4 - address at end of expected entries
+
+.data
+
+# number of test cases
+n:  .word 8
+ins:  .word
+        0,
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        10
+outs:  .word
+        # none,
+
+        1,
+
+        1,
+        1, 1,
+
+        1,
+        1, 1,
+        1, 2, 1,
+
+        1,
+        1, 1,
+        1, 2, 1,
+        1, 3, 3, 1,
+
+        1,
+        1, 1,
+        1, 2, 1,
+        1, 3, 3, 1,
+        1, 4, 6, 4, 1,
+
+        1,
+        1, 1,
+        1, 2, 1,
+        1, 3, 3, 1,
+        1, 4, 6, 4, 1,
+        1, 5, 10, 10, 5, 1,
+
+        1,
+        1, 1,
+        1, 2, 1,
+        1, 3, 3, 1,
+        1, 4, 6, 4, 1,
+        1, 5, 10, 10, 5, 1,
+        1, 6, 15, 20, 15, 6, 1,
+        1, 7, 21, 35, 35, 21, 7, 1,
+        1, 8, 28, 56, 70, 56, 28, 8, 1,
+        1, 9, 36, 84, 126, 126, 84, 36, 9, 1
+numouts:  .word
+        0,
+        1,
+        3,
+        6,
+        10,
+        15,
+        21,
+        55
+
+failmsg: .asciiz "failed for test input: "
+expectedmsg: .asciiz ". expected "
+tobemsg: .asciiz " to be "
+okmsg: .asciiz "all tests passed"
+prefix: .asciiz "["
+comma: .asciiz ", "
+suffix: .asciiz "]"
+
+.eqv BUFFER_SIZE 220
+
+.text
+
+runner:
+        lw      $s0, n
+        la      $s1, ins
+        la      $s2, outs
+        la      $s3, numouts
+
+        li      $v0, 9                  # code for allocating heap memory
+        li      $a0, BUFFER_SIZE        # specify length of longest expected output
+        syscall
+        move    $s4, $v0                # location of allocated memory is where callee writes result
+
+run_test:
+        jal     clear_output            # zero out output location
+
+        lw      $a0, 0($s1)             # load input value into a0
+        move    $a1, $s4                # load output location
+        jal     rows                    # call subroutine under test
+        move    $v1, $v0                # move return value in v0 to v1 because we need v0 for syscall
+        lw      $t5, 0($s3)             # expected number of entries
+        bne     $v1, $t5, exit_fail     # check if we have the expected number of entries
+
+        move    $t0, $s2                # address of expected entry
+        move    $t2, $s4                # address of actual entry
+        sll     $t4, $t5, 2             # number of bytes occupied by entries
+        add     $t4, $t4, $s2           # address at end of expected entries
+        beq     $t5, $zero, done_scan
+
+scan:
+        lw      $t1, 0($t0)             # load expected entry
+        lw      $t3, 0($t2)             # load actual entry
+        bne     $t1, $t3, exit_fail     # check if we have the expected entry
+        addi    $t0, $t0, 4             # advance to next expected entry
+        addi    $t2, $t2, 4             # advance to next actual entry
+        bne     $t0, $t4, scan          # repeat until all entries have been compared
+
+done_scan:
+        addi    $s1, $s1, 4             # point to next input word
+        move    $s2, $t4                # point to next expected entries
+        addi    $s3, $s3, 4             # point to next expected number of entries
+        sub     $s0, $s0, 1             # decrement num of tests left to run
+        bgt     $s0, $zero, run_test    # if more than zero tests to run, jump to run_test
+
+exit_ok:
+        la      $a0, okmsg              # put address of okmsg into a0
+        li      $v0, 4                  # 4 is print string
+        syscall
+
+        li      $v0, 10                 # 10 is exit with zero status (clean exit)
+        syscall
+
+exit_fail:
+        la      $a0, failmsg            # put address of failmsg into a0
+        li      $v0, 4                  # 4 is print string
+        syscall
+
+        lw      $a0, 0($s1)             # print input that failed on
+        li      $v0, 1                  # 1 -> "print integer"
+        syscall
+
+        la      $a0, expectedmsg
+        li      $v0, 4
+        syscall
+
+        move    $a0, $v1                # actual number of entries
+        move    $a1, $s4                # address of actual entries
+        jal     print_array
+
+        la      $a0, tobemsg
+        li      $v0, 4
+        syscall
+
+        lw      $a0, 0($s3)             # expected number of entries
+        move    $a1, $s2                # address of expected entries
+        jal     print_array
+
+        li      $a0, 1                  # set error code to 1
+        li      $v0, 17                 # 17 is exit with error
+        syscall
+
+
+clear_output:
+        sw      $zero, 0($s4)           # zero out output by storing 4 words (16 bytes) of zeros
+        sw      $zero, 4($s4)
+        sw      $zero, 8($s4)
+        sw      $zero, 12($s4)
+        jr      $ra
+
+
+print_array:
+                                        # print array with word count $a0, address $a1
+                                        # local variable s0 points to current element
+                                        # local variable s1 point to end of array
+
+        addi    $sp, $sp, -8            # Save existing values of $s0 and $s1
+        sw      $s0, 4($sp)
+        sw      $s1, 0($sp)
+
+        move    $s0, $a1                # first element of array
+        sll     $s1, $a0, 2             # length of array, in bytes
+        add     $s1, $s1, $a1           # pointer to end of array
+
+        la      $a0, prefix             # print prefix
+        li      $v0, 4
+        syscall
+
+        beq     $s0, $s1, output_suffix # jump ahead if array is empty
+        j       output_element          # first element is not preceeded by comma
+
+output_comma:
+        la      $a0, comma
+        li      $v0, 4
+        syscall
+
+output_element:
+        lw      $a0, 0($s0)             # load element value
+        addi    $s0, $s0, 4             # increment pointer
+        li      $v0, 1                  # 1 -> "print integer"
+        syscall
+
+        bne     $s0, $s1, output_comma  # repeat until we reach end of array
+
+output_suffix:
+        la      $a0, suffix
+        li      $v0, 4
+        syscall
+
+        lw      $s1, 0($sp)             # Restore original values of $s0 and $s1
+        lw      $s0, 4($sp)
+        addi    $sp, $sp, 8
+
+        jr      $ra
+
+# # Include your implementation here if you wish to run this from the MARS GUI.
+#.include "impl.mips"