1 files changed, 114 insertions, 55 deletions
diff --git a/2023/day17.rs b/2023/day17.rs
index 37aff45..57a4577 100644
--- a/2023/day17.rs
+++ b/2023/day17.rs
@@ -5,86 +5,145 @@ use num::complex::Complex as c;
 use num::Complex;
 use std::cmp::min;
 use std::collections::HashMap;
+use std::collections::HashSet;
 use std::fs::File;
 use std::io::Read;
 
 type Matrix<T> = Vec<Vec<T>>;
 
-fn rec(
-    pos: Complex<i32>,
-    dir: Complex<i32>,
-    conti: u32,
-    mut hl: i32,
-    s: &mut HashMap<(Complex<i32>, Complex<i32>, u32), i32>,
-    m: &Matrix<i32>,
-) -> i32 {
-    if !(0 <= pos.re && pos.re < m[0].len() as i32 && 0 <= pos.im && pos.im < m.len() as i32) {
-        return 999999999;
-    }
-    hl += m[pos.im as usize][pos.re as usize];
-
-    if conti > 3 {
-        return 999999999;
-    }
-
-    // println!("{}", pos);
-    if let Some(hl_) = s.get(&(pos, dir, conti)) {
-        if hl_ <= &hl {
-            return 999999999;
+fn bfs1(m: &Matrix<u32>) -> u32 {
+    let mut s: HashMap<(Complex<i32>, Complex<i32>, u32), u32> = HashMap::new();
+    let mut hs: HashSet<(Complex<i32>, Complex<i32>, u32, u32)> = HashSet::new();
+    let mut hs_next: HashSet<(Complex<i32>, Complex<i32>, u32, u32)> = HashSet::new();
+
+    hs.insert((c::new(0, 0), c::new(1, 0), 0, 0));
+
+    let mut res: Vec<u32> = Vec::new();
+    while hs.len() > 0 {
+        for (pos, dir, conti, mut hl) in hs {
+            if conti > 2 {
+                continue;
+            }
+
+            if !(0 <= pos.re
+                && pos.re < m[0].len() as i32
+                && 0 <= pos.im
+                && pos.im < m.len() as i32)
+            {
+                continue;
+            }
+
+            hl += m[pos.im as usize][pos.re as usize];
+
+            if pos == c::new(m[0].len() as i32 - 1, m.len() as i32 - 1) {
+                res.push(hl);
+                continue;
+            }
+
+            if let Some(hl_) = s.get(&(pos, dir, conti)) {
+                if hl_ <= &hl {
+                    continue;
+                }
+            }
+            s.insert((pos, dir, conti), hl);
+
+            let new_dir = dir;
+            let new_pos = pos + new_dir;
+            hs_next.insert((new_pos, new_dir, conti + 1, hl));
+
+            let new_dir = dir * c::i();
+            let new_pos = pos + new_dir;
+            hs_next.insert((new_pos, new_dir, 0, hl));
+
+            let new_dir = dir * (-c::i());
+            let new_pos = pos + new_dir;
+            hs_next.insert((new_pos, new_dir, 0, hl));
         }
+        hs = hs_next;
+        hs_next = HashSet::new();
     }
-    s.insert((pos, dir, conti), hl);
+    return res.into_iter().fold(999999999, min) - m[0][0];
+}
 
-    if pos == c::new(m[0].len() as i32 - 1, m.len() as i32 - 1) {
-        return hl;
+fn bfs2(m: &Matrix<u32>) -> u32 {
+    let mut s: HashMap<(Complex<i32>, Complex<i32>, u32), u32> = HashMap::new();
+    let mut hs: HashSet<(Complex<i32>, Complex<i32>, u32, u32)> = HashSet::new();
+    let mut hs_next: HashSet<(Complex<i32>, Complex<i32>, u32, u32)> = HashSet::new();
+
+    hs.insert((c::new(0, 0), c::new(1, 0), 0, 0));
+
+    let mut res: Vec<u32> = Vec::new();
+    while hs.len() > 0 {
+        for (pos, dir, conti, mut hl) in hs {
+            if conti > 9 {
+                continue;
+            }
+
+            if !(0 <= pos.re
+                && pos.re < m[0].len() as i32
+                && 0 <= pos.im
+                && pos.im < m.len() as i32)
+            {
+                continue;
+            }
+
+            hl += m[pos.im as usize][pos.re as usize];
+
+            if conti > 2 && pos == c::new(m[0].len() as i32 - 1, m.len() as i32 - 1) {
+                res.push(hl);
+                continue;
+            }
+
+            if let Some(hl_) = s.get(&(pos, dir, conti)) {
+                if hl_ <= &hl {
+                    continue;
+                }
+            }
+            s.insert((pos, dir, conti), hl);
+
+            let new_dir = dir;
+            let new_pos = pos + new_dir;
+            hs_next.insert((new_pos, new_dir, conti + 1, hl));
+
+            if conti > 2 {
+                let new_dir = dir * c::i();
+                let new_pos = pos + new_dir;
+                hs_next.insert((new_pos, new_dir, 0, hl));
+
+                let new_dir = dir * (-c::i());
+                let new_pos = pos + new_dir;
+                hs_next.insert((new_pos, new_dir, 0, hl));
+            }
+        }
+        hs = hs_next;
+        hs_next = HashSet::new();
     }
-
-    let mut ret = 999999999;
-    let new_pos = pos + dir;
-    let new_dir = dir;
-    ret = min(ret, rec(new_pos, new_dir, conti + 1, hl, s, m));
-
-    let new_pos = pos + dir;
-    let new_dir = dir * c::i();
-    ret = min(ret, rec(new_pos, new_dir, 0, hl, s, m));
-
-    let new_pos = pos + dir;
-    let new_dir = dir * (-c::i());
-    ret = min(ret, rec(new_pos, new_dir, 0, hl, s, m));
-
-    return ret;
+    return res.into_iter().fold(999999999, min) - m[0][0];
 }
 
 fn main() {
-    let filename = "in/day17.ref";
-    // let filename = "in/day17.pzl";
+    // let filename = "in/day17.ref";
+    let filename = "in/day17.pzl";
 
     let mut f = File::open(filename).expect("cannot open file");
     let mut content = String::new();
     f.read_to_string(&mut content).expect("cannot read file");
     let lines = content.trim_end().split('\n');
-    // println!("{:?}", lines);
 
-    let mut m: Matrix<i32> = Vec::new();
+    let mut m: Matrix<u32> = Vec::new();
     for line in lines {
-        let mut mr: Vec<i32> = Vec::new();
+        let mut mr: Vec<u32> = Vec::new();
         for c in line.chars() {
-            mr.push(c.to_digit(10).unwrap() as i32);
+            mr.push(c.to_digit(10).unwrap());
         }
         m.push(mr);
     }
-    // println!("{:?}", m);
-
-    let mut state: HashMap<(Complex<i32>, Complex<i32>, u32), i32> = HashMap::new();
-    let mut pos = c::new(0, 0);
-    let mut dir = c::new(1, 0);
-
-    let res1 = rec(pos, dir, 0, 0, &mut state, &m);
-    // println!("{:?}", state);
 
-    let mut res2 = 0;
+    let res1 = bfs1(&m);
+    let res2 = bfs2(&m);
 
     println!("res1: {}", res1);
     println!("res2: {}", res2);
+    assert_eq!(res1, 635);
+    assert_eq!(res2, 734);
 }
-// 612 too low