Project euler questions

Author: Narahari-Sundaragopalan

exercises/misc/largestProduct.js

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+/*
+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
+71636269561882670428252483600823257530420752963450
+
+Find the thirteen adjacent digits in the 1000-digit number that have the greatest product.
+What is the value of this product?
+*/
+
+function findLargestProduct() {
+  digitString =
+    '7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450';
+  let largestProduct = 0;
+  for (let i = 0; i < digitString.length - 13; i++) {
+    let product = 1;
+
+    for (let j = i; j < i + 13; j++) {
+      product *= parseInt(digitString[j]);
+    }
+
+    if (product > largestProduct) {
+      largestProduct = product;
+    }
+  }
+
+  return largestProduct;
+}

exercises/misc/primeSummation.js

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+/*
+The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
+
+Find the sum of all the primes below two million.
+*/
+
+function summationPrimes() {
+  const maxPrime = 10;
+  let j = 2;
+  let sum = 0;
+
+  for (let i = 2; i < maxPrime; i++) {
+    while (i % j !== 0) {
+      j++;
+
+      if (i === j) {
+        sum += i;
+        break;
+      }
+    }
+    j = 2;
+  }
+
+  return sum;
+}

exercises/misc/pythagoreanTriplet.js

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+/*
+A Pythagorean triplet is a set of three natural numbers, a < b < c, for which,
+
+a2 + b2 = c2
+For example, 32 + 42 = 9 + 16 = 25 = 52.
+
+There exists exactly one Pythagorean triplet for which a + b + c = 1000.
+Find the product abc.
+*/
+
+function pythagoreanTriplet() {
+  const sum = 1000;
+  let product = 0;
+
+  for (let a = 1; a <= sum / 3; a++) {
+    for (let b = a + 1; b <= sum / 2; b++) {
+      let c = sum - a - b;
+      if (c * c === a * a + b * b) {
+        product = a * b * c;
+        break;
+      }
+    }
+  }
+
+  return product;
+}