欧拉计划＃8 — Javascript

Question

 /*** * Problem 8 -- Largest Product in a Series * * @author RepeaterCreeper */ var grid = `73167176531330624919225119674426574742355349194934 96983520312774506326239578318016984801869478851843 85861560789112949495459501737958331952853208805511 12540698747158523863050715693290963295227443043557 66896648950445244523161731856403098711121722383113 62229893423380308135336276614282806444486645238749 30358907296290491560440772390713810515859307960866 70172427121883998797908792274921901699720888093776 65727333001053367881220235421809751254540594752243 52584907711670556013604839586446706324415722155397 53697817977846174064955149290862569321978468622482 83972241375657056057490261407972968652414535100474 82166370484403199890008895243450658541227588666881 16427171479924442928230863465674813919123162824586 17866458359124566529476545682848912883142607690042 24219022671055626321111109370544217506941658960408 07198403850962455444362981230987879927244284909188 84580156166097919133875499200524063689912560717606 05886116467109405077541002256983155200055935729725 71636269561882670428252483600823257530420752963450`; /** * Largest Adjacent Numbers * * @returns int */ function largestAdjacentNumbers(grid, consecutiveLength = 4, separator = "\\n") { let gridData = grid.split("\\n"), largestProduct = 0; for (var row in gridData) { currentRow = gridData[row].split('').map(x => parseInt(x)); for (var i = 0; i < currentRow.length - consecutiveLength; i++) { combination = currentRow.slice(i, i + consecutiveLength); if (!combination.includes(0)) { product = combination.reduce(function(a, b) { return a * b }); if (largestProduct < product) largestProduct = product; } } } return largestProduct; } console.log(largestAdjacentNumbers(grid, 13)); 

Issue:

So the issue the fact that no matter what I do, my code is stuck at getting:

The correct answer is:


As you can see that's a MASSIVE difference. If I simply do a 4-adjacent number in the grid, it works as it matches the solution given for the 4-adjacent number example. Which is:

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I've definitely looked into some other SO questions that relate to Problem 8 of Project Euler, but none of them seem to match my issue. If I did somehow miss one, a link would be nice. Though I do doubt that as I literally went through a good bit of SO questions before posting this.

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Problem States:

https://projecteuler.net/problem=8 -- Link to Problem

The four adjacent digits in the 1000-digit number that have the greatest product are 9 × 9 × 8 × 9 = 5832.

73167176531330624919225119674426574742355349194934 96983520312774506326239578318016984801869478851843 85861560789112949495459501737958331952853208805511 12540698747158523863050715693290963295227443043557 66896648950445244523161731856403098711121722383113 62229893423380308135336276614282806444486645238749 30358907296290491560440772390713810515859307960866 70172427121883998797908792274921901699720888093776 65727333001053367881220235421809751254540594752243 52584907711670556013604839586446706324415722155397 53697817977846174064955149290862569321978468622482 83972241375657056057490261407972968652414535100474 82166370484403199890008895243450658541227588666881 16427171479924442928230863465674813919123162824586 17866458359124566529476545682848912883142607690042 24219022671055626321111109370544217506941658960408 07198403850962455444362981230987879927244284909188 84580156166097919133875499200524063689912560717606 05886116467109405077541002256983155200055935729725 7163626956188267042825248360082 3257530420752963450

Find the thirteen adjacent digits in the 1000-digit number that have the greatest product. What is the value of this product?

Answer 1

The question says:

The four adjacent digits in the 1000-digit number that have the greatest product are 9 × 9 × 8 × 9 = 5832.

(some number over multiple lines, 1000 digits long)

Find the thirteen adjacent digits in the 1000-digit number that have the greatest product. What is the value of this product?

It's not asking you to iterate over each row - it's asking you to interpret the whole thing as one string (or number) and compare adjacent digits. Turn the grid into a single string initially, and your code works as expected:

 var grid = `73167176531330624919225119674426574742355349194934 96983520312774506326239578318016984801869478851843 85861560789112949495459501737958331952853208805511 12540698747158523863050715693290963295227443043557 66896648950445244523161731856403098711121722383113 62229893423380308135336276614282806444486645238749 30358907296290491560440772390713810515859307960866 70172427121883998797908792274921901699720888093776 65727333001053367881220235421809751254540594752243 52584907711670556013604839586446706324415722155397 53697817977846174064955149290862569321978468622482 83972241375657056057490261407972968652414535100474 82166370484403199890008895243450658541227588666881 16427171479924442928230863465674813919123162824586 17866458359124566529476545682848912883142607690042 24219022671055626321111109370544217506941658960408 07198403850962455444362981230987879927244284909188 84580156166097919133875499200524063689912560717606 05886116467109405077541002256983155200055935729725 71636269561882670428252483600823257530420752963450` .split('\\n').join(''); /** * Largest Adjacent Numbers * * @returns int */ function largestAdjacentNumbers(grid, consecutiveLength = 4, separator = "\\n") { let gridData = grid.split("\\n"), largestProduct = 0; for (var row in gridData) { currentRow = gridData[row].split('').map(x => parseInt(x)); for (var i = 0; i < currentRow.length - consecutiveLength; i++) { combination = currentRow.slice(i, i + consecutiveLength); if (!combination.includes(0)) { product = combination.reduce(function(a, b) { return a * b }); if (largestProduct < product) largestProduct = product; } } } return largestProduct; } console.log(largestAdjacentNumbers(grid, 13)); 

But it would be good to remove the part that iterates over each row now that there are no rows or newlines in the input, and to fix the off-by-one error, as noted in comment:

 var grid = `73167176531330624919225119674426574742355349194934 96983520312774506326239578318016984801869478851843 85861560789112949495459501737958331952853208805511 12540698747158523863050715693290963295227443043557 66896648950445244523161731856403098711121722383113 62229893423380308135336276614282806444486645238749 30358907296290491560440772390713810515859307960866 70172427121883998797908792274921901699720888093776 65727333001053367881220235421809751254540594752243 52584907711670556013604839586446706324415722155397 53697817977846174064955149290862569321978468622482 83972241375657056057490261407972968652414535100474 82166370484403199890008895243450658541227588666881 16427171479924442928230863465674813919123162824586 17866458359124566529476545682848912883142607690042 24219022671055626321111109370544217506941658960408 07198403850962455444362981230987879927244284909188 84580156166097919133875499200524063689912560717606 05886116467109405077541002256983155200055935729725 71636269561882670428252483600823257530420752963450`; var gridData = grid.split('\\n').join('').split('').map(Number); /** * Largest Adjacent Numbers * * @returns int */ function largestAdjacentNumbers(grid, consecutiveLength = 4, separator = "\\n") { let largestProduct = 0; for (var i = 0; i <= gridData.length - consecutiveLength; i++) { combination = gridData.slice(i, i + consecutiveLength); if (!combination.includes(0)) { const product = combination.reduce(function(a, b) { return a * b }); if (largestProduct < product) largestProduct = product; } } return largestProduct; } console.log(largestAdjacentNumbers(grid, 13)); 

Answer 2

The problem apparently doesn't intend that the end of line has any meaning. Here is code that produces the desired result.

 let str = `73167176531330624919225119674426574742355349194934 96983520312774506326239578318016984801869478851843 85861560789112949495459501737958331952853208805511 12540698747158523863050715693290963295227443043557 66896648950445244523161731856403098711121722383113 62229893423380308135336276614282806444486645238749 30358907296290491560440772390713810515859307960866 70172427121883998797908792274921901699720888093776 65727333001053367881220235421809751254540594752243 52584907711670556013604839586446706324415722155397 53697817977846174064955149290862569321978468622482 83972241375657056057490261407972968652414535100474 82166370484403199890008895243450658541227588666881 16427171479924442928230863465674813919123162824586 17866458359124566529476545682848912883142607690042 24219022671055626321111109370544217506941658960408 07198403850962455444362981230987879927244284909188 84580156166097919133875499200524063689912560717606 05886116467109405077541002256983155200055935729725 71636269561882670428252483600823257530420752963450`; str = str.replace(/\\n/g, ""); let max = 0; for (let i = 0; i < str.length - 12; i++) { let part = str.substr(i, 13); let currentProduct = 1; for (let n of part) { currentProduct *= +n; } max = Math.max(max, currentProduct); } console.log(max);