day 7 simplify awk solution

inspired by elly's fennel solution

day07/sol.awk

@@ -4,21 +4,10 @@ BEGIN { depth = 0 }
 
 /^\$/ { cmd = $2 }
 
-/^\$ cd/ {
-    if ($3 == "/") {
-        depth = 0
-    } else if ($3 == "..") {
-        depth -= 1
-    } else {
-        cwd[depth++] = $3
-    }
-    #print dir
-    next
-}
-
-/^\$ ls$/ {
-    next
-}
+/^\$ cd \/$/    { depth = 0; next }
+/^\$ cd \.\.$/  { depth -= 1; next }
+/^\$ cd/        { cwd[depth++] = $3; next }
+/^\$ ls$/       { next }
 
 function add(sz) {
     sizes["/"] += sz
@@ -29,11 +18,9 @@ function add(sz) {
     }
 }
 
-cmd == "ls" {
-    if ($1 != "dir") {
-        #print(dir "/" $2, $1)
-        add($1)
-    }
+cmd == "ls" && $1 != "dir" {
+    #print(dir "/" $2, $1)
+    add($1)
 }
 
 END {