Handle the unseen case of no wins

1 files changed, 15 insertions, 12 deletions

diff --git a/06/src/stuff.rs b/06/src/stuff.rs
index b3651ab..aa1d53d 100644
--- a/06/src/stuff.rs
+++ b/06/src/stuff.rs
@@ -20,26 +20,29 @@ fn distance(c: u64, n: u64) -> u64 {
     n.saturating_sub(c)*c
 }
 
-pub fn num_solutions(time: u64, record: u64) -> u64 {
-    //println!("Time avail: {}. Record: {}.", time, record);
-    
+fn winning_interval(time: u64, record: u64) -> Option<(u64, u64)> {
     let (est_l, est_u) = root_estimate(time, record);
-    //println!("Estimate: [{}, {}]", est_l, est_u);
-
+    
     // Find highest charge time that does not beat the record, looking downwards from lower estimate.
     let l0 = (0..=est_l).rev().into_iter().find(|& charge| distance(charge, time) <= record).unwrap_or(0);
     // Find lowest charge time that does beat the record, looking upwards from the above.
-    let l1 = (l0..=est_u).into_iter().find(|& charge| distance(charge, time) > record).unwrap_or(l0);
-
+    let l1 = (l0..=est_u).into_iter().find(|& charge| distance(charge, time) > record)?;
+    
     // Find lowest charge time that does not beat the record, looking upwards from upper estimate.
     let u0 = (est_u..).into_iter().find(|& charge| distance(charge, time) <= record).unwrap_or(time);
     // Find the highest charge time that does beat the record, looking downwards from the above.
-    let u1 = (l1..=u0).rev().into_iter().find(|& charge| distance(charge, time) > record).unwrap_or(l1);
-
-    //println!("Winning range: [{}, {}]", l1, u1);
-    //println!("....");
+    let u1 = (l1..=u0).rev().into_iter().find(|& charge| distance(charge, time) > record)?;
     
-    u1.saturating_sub(l1) + 1
+    Some((l1, u1))
+}
+
+pub fn num_solutions(time: u64, record: u64) -> u64 {   
+    if let Some((l, u)) = winning_interval(time, record) {
+        (u - l) + 1
+    }
+    else {
+        0
+    }
 }
 
 pub fn ascii_to_u64(s: & [u8]) -> u64 {