From 255a2911a2206376a85242443a6a7a107d6dbe42 Mon Sep 17 00:00:00 2001
From: Mistivia <i@mistivia.com>
Date: Mon, 23 Dec 2024 14:23:42 +0800
Subject: day 10 part 2

---
 10/2.tcl | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 10/2.tcl

diff --git a/10/2.tcl b/10/2.tcl
new file mode 100644
index 0000000..fecbe7f
--- /dev/null
+++ b/10/2.tcl
@@ -0,0 +1,56 @@
+set fp [open "input" r]
+set line {}
+while {[gets $fp line] >= 0} {
+    lappend lines $line
+}
+close $fp
+
+set height [llength $lines]
+set width [string length [lindex $lines 0]]
+
+proc out_of_range {x y} {
+    global height width
+    if {$x < 0 || $x >= $width} {
+        return 1
+    }
+    if {$y < 0 || $y >= $height} {
+        return 1
+    }
+    return 0
+}
+
+proc char_at {x y} {
+    global lines
+    if {[out_of_range $x $y]} {
+        return -1
+    }
+    return [string index [lindex $lines $y] $x]
+}
+
+proc find_path {x y expect} {
+    global path_cache
+    if {[out_of_range $x $y]} {
+        return 0
+    }
+    if {$expect != [char_at $x $y]} {
+        return 0
+    }
+    if {$expect == 9} {
+        return 1
+    }
+    set next [expr {$expect + 1}]
+    set ret [expr {
+        [find_path [expr {$x + 1}] $y $next]
+        + [find_path [expr {$x - 1}] $y $next]
+        + [find_path $x [expr {$y + 1}] $next]
+        + [find_path $x [expr {$y - 1}] $next]
+    }]
+}
+
+set sum 0
+for {set x 0} {$x < $width} {incr x} {
+    for {set y 0} {$y < $height} {incr y} {
+        incr sum [find_path $x $y 0]
+    }
+}
+puts $sum
-- 
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