I have resolved the Problem 8 of Project Euler;
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?
Below is the part of my code which I need explanation for.
long product = 1;
for (i = 0; i < num.length() - 13; i++) {
for (int j = i; j <= i + 12; j++) {
product = (num.charAt(j) - 48) * product; //num is the original number provided in the problem statement.
}
}
Earlier, I wrote this Piece of code without subtracting 48, but I was getting wrong answer. Then I searched online and saw that someone used the same approach as mine to resolve the problem, only difference is that they put -48 in the code, I too put -48 and voila! got the correct answer.
Someone please explain why is -48 worked? and what it is for?
You work on chars:
'0' is 48,
'1' is 49 ...
and so on in ASCII, so substracting 48 will translate char to integer.