project-euler/projectEuler008.cpp at master · perfectsimulation/project-euler · GitHub

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/*	Problem 8
	Largest Product in a Series

	The four adjacent digits in the following 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?
*/

#include <iomanip>
#include <iostream>
#include <string>

using namespace std;

void main () {
	string numberSeries =
	"73167176531330624919225119674426574742355349194934"
	"96983520312774506326239578318016984801869478851843"
	"85861560789112949495459501737958331952853208805511"
	"12540698747158523863050715693290963295227443043557"
	"66896648950445244523161731856403098711121722383113"
	"62229893423380308135336276614282806444486645238749"
	"30358907296290491560440772390713810515859307960866"
	"70172427121883998797908792274921901699720888093776"
	"65727333001053367881220235421809751254540594752243"
	"52584907711670556013604839586446706324415722155397"
	"53697817977846174064955149290862569321978468622482"
	"83972241375657056057490261407972968652414535100474"
	"82166370484403199890008895243450658541227588666881"
	"16427171479924442928230863465674813919123162824586"
	"17866458359124566529476545682848912883142607690042"
	"24219022671055626321111109370544217506941658960408"
	"07198403850962455444362981230987879927244284909188"
	"84580156166097919133875499200524063689912560717606"
	"05886116467109405077541002256983155200055935729725"
	"71636269561882670428252483600823257530420752963450";

	int adjacentDigits = 13;
	float greatestProduct = 0;
	float currentProduct = 1;
	int lastIndex = adjacentDigits - 1;

	while (lastIndex < numberSeries.length ()) {
		currentProduct = 1;

		for (int i = lastIndex - adjacentDigits + 1; i <= lastIndex; i++) {
			int num_int = numberSeries [i] - 48;	// char to int
			float num = float(num_int);				// int to float
			currentProduct *= num;
		}

		if (currentProduct > greatestProduct) {
			greatestProduct = currentProduct;
		}

		lastIndex++;
	}

	cout << setprecision (0) << fixed;
	cout << greatestProduct << endl;
}