diff --git a/Project-Euler/Problem2.js b/Project-Euler/Problem2.js new file mode 100644 index 000000000..ed3c30c7c --- /dev/null +++ b/Project-Euler/Problem2.js @@ -0,0 +1,15 @@ +const SQ5 = 5 ** .5; // Square root of 5 +const PHI = (1 + SQ5) / 2; // definition of PHI + +//theoretically it should take O(1) constant amount of time as long +// arithmetic calculations are considered to be in constant amount of time. + +function EvenFibonacci(limit) { + const highestIndex = Math.floor(Math.log(limit * SQ5) / Math.log(PHI)); + const n = Math.floor(highestIndex / 3); + return ((PHI ** (3 * n + 3) - 1) / (PHI ** 3 - 1) + - ((1 - PHI) ** (3 * n + 3) - 1) / ((1 - PHI) ** 3 - 1)) / SQ5; +} + +console.log(EvenFibonacci(4e6)); +// Sum of Even Fibonnaci upto 4 Million \ No newline at end of file