feat(problem): 8 - largest product in a series

src/bin/8.rs

@@ -0,0 +1,78 @@
+/*
+Problem 8 - Largest product in a series
+
+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?
+*/
+
+const NUMBER: &str = "7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450";
+
+const ADJACENT_DIGITS: usize = 13;
+
+fn largest_product(number: &str, adjacent_digits: usize) -> usize {
+	if adjacent_digits > number.len() {
+		panic!("I can not check for the product of {} adjacent digits when there is only {} digits in the number!", adjacent_digits, number.len());
+	}
+
+	let mut cursor_index = 0;
+	let mut selections: Vec<Vec<u32>> = vec![];
+	let characters = number.chars().collect::<Vec<char>>();
+
+	while cursor_index < number.len() {
+		let mut selection: Vec<u32> = vec![];
+
+		for i in 0..adjacent_digits {
+			if cursor_index + i >= number.len() - 1 {
+				break;
+			}
+
+			selection.push(characters[cursor_index + i].to_digit(10).unwrap());
+		}
+
+		selections.push(selection);
+		cursor_index += 1;
+	}
+
+	let mut products: Vec<usize> = vec![];
+
+	for i in 0..selections.len() {
+		let mut product: usize = 1;
+
+		for value in &selections[i] {
+			product *= *value as usize;
+		}
+
+		products.push(product);
+	}
+
+	products.sort();
+	products.reverse();
+
+	return products[0];
+}
+
+fn main() {
+	let value = largest_product(NUMBER, ADJACENT_DIGITS);
+	
+	println!("The thirteen adjacent digits in the number that have the greatest product have a product of {value}");
+}