day 2

past-solutions/2-1.rs

@@ -0,0 +1,120 @@
+use std::io::Read;
+use std::iter;
+use std::num::{NonZero, NonZeroU32};
+
+fn main() {
+    let mut problem = parse_problem();
+
+    println!("Parsed problem: {:?}", problem);
+
+    println!("Count in total: {}", compute_problem(&mut problem))
+}
+
+#[derive(Debug)]
+struct Problem{
+    ranges: Vec<(u64, u64)>
+}
+
+#[derive(Debug)]
+struct CleanedProblem{
+    ranges: Vec<(u64, u64, NonZeroU32)>
+}
+
+fn parse_problem() -> Problem {
+    let mut input = String::new();
+    std::io::stdin().read_to_string(&mut input).expect("Failed to read input");
+
+    let ranges = input.split(',').
+        map(|x| x.split_once('-').expect("dash in there"))
+        .map(|x| (x.0.parse::<u64>().expect("Parse error on 0"), x.1.parse::<u64>().expect("Parse error on 1")))
+        .collect::<Vec<_>>();
+
+    return Problem{
+        ranges,
+    };
+}
+
+fn compute_problem(problem: &mut Problem) -> u64 {
+    //Potentialy ensure it is not overlapping
+    let problem = clean_problem(problem);
+
+    println!("Cleaned problem: {:?}", problem);
+
+    let count = problem.ranges.iter().map(|range| compute_range(range.0, range.1)).sum::<u64>();
+
+    return count;
+}
+
+fn clean_problem(problem: &Problem) -> CleanedProblem {
+    let new_ranges = problem.ranges.iter().map(|(lower, upper)|{
+        if (upper < lower){
+            return vec![]
+        }
+
+        let digitCountU = count_digits(*upper);
+        let digitCountL = count_digits(*lower);
+
+        if (digitCountL == digitCountU){
+            return vec![(*lower, *upper, digitCountU)];
+        }
+
+        let lowestOfDegree = lowestOfDegree(digitCountU);
+
+        return vec![(*lower, lowestOfDegree-1, digitCountL), (lowestOfDegree, *upper, digitCountU)];
+    }).flatten().collect::<Vec<_>>();
+
+  return CleanedProblem{ranges: new_ranges};
+}
+
+fn lowestOfDegree(degree : NonZeroU32) -> u64{
+    10u64.pow(degree.get() - 1)
+}
+
+fn compute_range(lower_bound: u64, upper_bound: u64) -> u64 {
+    assert!(lower_bound > 0 && upper_bound > 0);
+    assert!(upper_bound > lower_bound);
+    assert!(count_digits(upper_bound) == count_digits(lower_bound));
+
+    let digitCount = count_digits(upper_bound);
+
+    if digitCount.get() % 2 != 0{
+        return 0;
+    }
+
+
+    let halfDigitCount = NonZeroU32::new(digitCount.get() / 2).unwrap();
+
+
+
+    let mut half = (lower_bound / 10u64.pow(halfDigitCount.get())).min(lower_bound % 10u64.pow(halfDigitCount.get()));
+    let mut count = 0;
+
+    loop{
+        let whole = combine_numbers(half, halfDigitCount);
+        if whole >= lower_bound && whole <= upper_bound{
+            count += whole;
+        }else if whole > upper_bound{
+            break;
+        }
+
+        half += 1;
+    }
+
+    return count;
+}
+
+fn count_digits(mut n : u64) -> NonZeroU32{
+    assert!(n > 0);
+    let mut count = 0u64;
+
+    while (n != 0){
+        n = n / 10;
+        count +=1 ;
+    }
+
+    return unsafe{NonZeroU32::new_unchecked(count as u32)};
+}
+
+fn combine_numbers(half : u64, degree : NonZeroU32) -> u64 {
+    return half + half * 10u64.pow(degree.get() as u32)
+}