Sync largest-series-product docs with problem-specifications

exercises/practice/largest-series-product/.docs/instructions.md

@@ -1,19 +1,26 @@
 # Instructions
 
-Given a string of digits, calculate the largest product for a contiguous substring of digits of length n.
+Your task is to look for patterns in the long sequence of digits in the encrypted signal.
 
-For example, for the input `'1027839564'`, the largest product for a series of 3 digits is 270 `(9 * 5 * 6)`, and the largest product for a series of 5 digits is 7560 `(7 * 8 * 3 * 9 * 5)`.
+The technique you're going to use here is called the largest series product.
 
-Note that these series are only required to occupy *adjacent positions* in the input; the digits need not be *numerically consecutive*.
+Let's define a few terms, first.
 
-For the input `'73167176531330624919225119674426574742355349194934'`,
-the largest product for a series of 6 digits is 23520.
+- **input**: the sequence of digits that you need to analyze
+- **series**: a sequence of adjacent digits (those that are next to each other) that is contained within the input
+- **span**: how many digits long each series is
+- **product**: what you get when you multiply numbers together
 
-For a series of zero digits, you need to return the empty product (the result of multiplying no numbers), which is 1.
+Let's work through an example, with the input `"63915"`.
 
-~~~~exercism/advanced
-You do not need to understand why the empty product is 1 to solve this problem,
-but in case you are interested, here is an informal argument: if we split a list of numbers `A` into two new lists `B` and `C`, then we expect `product(A) == product(B) * product(C)` because we don't expect the order that you multiply things to matter; now if we split a list containing only the number 3 into the empty list and a list containing the number 3 then the product of the empty list has to be 1 for `product([3]) == product([]) * product([3])` to be true.
-
-The same kind of argument justifies why the sum of no numbers is 0.
-~~~~
+- To form a series, take adjacent digits in the original input.
+- If you are working with a span of `3`, there will be three possible series:
+  - `"639"`
+  - `"391"`
+  - `"915"`
+- Then we need to calculate the product of each series:
+  - The product of the series `"639"` is 162 (`6 × 3 × 9 = 162`)
+  - The product of the series `"391"` is 27 (`3 × 9 × 1 = 27`)
+  - The product of the series `"915"` is 45 (`9 × 1 × 5 = 45`)
+- 162 is bigger than both 27 and 45, so the largest series product of `"63915"` is from the series `"639"`.
+  So the answer is **162**.

exercises/practice/largest-series-product/.docs/introduction.md

@@ -0,0 +1,5 @@
+# Introduction
+
+You work for a government agency that has intercepted a series of encrypted communication signals from a group of bank robbers.
+The signals contain a long sequence of digits.
+Your team needs to use various digital signal processing techniques to analyze the signals and identify any patterns that may indicate the planning of a heist.

exercises/practice/largest-series-product/.meta/tests.toml

@@ -41,9 +41,11 @@ description = "rejects span longer than string length"
 
 [06bc8b90-0c51-4c54-ac22-3ec3893a079e]
 description = "reports 1 for empty string and empty product (0 span)"
+include = false
 
 [3ec0d92e-f2e2-4090-a380-70afee02f4c0]
 description = "reports 1 for nonempty string and empty product (0 span)"
+include = false
 
 [6d96c691-4374-4404-80ee-2ea8f3613dd4]
 description = "rejects empty string and nonzero span"

exercises/practice/largest-series-product/largest_series_product.bats

@@ -76,38 +76,6 @@ load bats-extra
     assert_output "$expected"
 }
 
-# There may be some confusion about whether this should be 1 or error.
-# The reasoning for it being 1 is this:
-# There is one 0-character string contained in the empty string.
-# That's the empty string itself.
-# The empty product is 1 (the identity for multiplication).
-# Therefore LSP('', 0) is 1.
-# It's NOT the case that LSP('', 0) takes max of an empty list.
-# So there is no error.
-# Compare against LSP('123', 4):
-# There are zero 4-character strings in '123'.
-# So LSP('123', 4) really DOES take the max of an empty list.
-# So LSP('123', 4) errors and LSP('', 0) does NOT.
-
-@test "reports 1 for empty string and empty product (0 span)" {
-    [[ $BATS_RUN_SKIPPED == "true" ]] || skip
-    run bash largest_series_product.sh 0
-    expected=1
-    assert_success
-    assert_output "$expected"
-}
-
-# As above, there is one 0-character string in '123'.
-# So again no error. It's the empty product, 1.
-
-@test "reports 1 for nonempty string and empty product (0 span)" {
-    [[ $BATS_RUN_SKIPPED == "true" ]] || skip
-    run bash largest_series_product.sh 123 0
-    expected=1
-    assert_success
-    assert_output "$expected"
-}
-
 # error cases
 
 @test "rejects span longer than string length" {