1 files changed, 21 insertions, 30 deletions

diff --git a/src/2022/day12/aoc.h b/src/2022/day12/aoc.h
index 3ac0c76..a7380b2 100644
--- a/src/2022/day12/aoc.h
+++ b/src/2022/day12/aoc.h
@@ -1,5 +1,6 @@
 #include "common.h"
 #include <vector>
+#include <deque>
 
 namespace aoc2022 {
 
@@ -84,36 +85,26 @@ struct heightmap {
      return space;
   };
 
-  void find_prev(int steps, pos p, std::vector<pos>& as) {
-    // printf("%s (%d,%d) %c\n", indent(steps), p.x, p.y, get(p));
-    if (get(p) == 'a') {
-      as.push_back(p);
-    }
-    else {
-      pos prev[4];
-      int n = 0;
-      get_prev(p, prev, &n);
-      for (int i = 0; i < n; i++) {
-        find_prev(steps + 1, prev[i], as);
-      }
-    }
-  }
-
-  void find(int steps, pos p, std::vector<int>& paths) {
-    // printf("%s (%d,%d) %c\n", indent(steps), p.x, p.y, get(p));
-    if (p == end) {
-      paths.push_back(steps);
-    }
-    else {
-      pos next[4];
-      int n = 0;
-      get_next(p, next, &n);
-      for(int i = 0; i < n; i++) {
-        was(next[i]) += 1;
-        find(steps + 1, next[i], paths);
-        was(next[i]) -= 1;
-      }
-    }
+  void find(pos p, std::vector<int>& paths) {
+     std::deque<pos> q = {p};
+     int steps{0};
+     while (!q.empty()) {
+        steps += 1;
+        pos px = q.front();
+        q.pop_front();
+        was(px) += 1;
+        pos ps[4];
+        int n{0};
+        get_prev(px, ps, &n);
+        for (int i = 0; i < n; i++) {
+          if (ps[i] == start) {
+            paths.push_back(steps);
+          }
+          else {
+             q.push_back(ps[i]);
+          }
+        }
+     }
   }
 
   void print() {