1 files changed, 90 insertions, 0 deletions
diff --git a/apps/advent2020/1b.mu b/apps/advent2020/1b.mu
new file mode 100644
index 00000000..7fdf75a6
--- /dev/null
+++ b/apps/advent2020/1b.mu
@@ -0,0 +1,90 @@
+fn main -> _/ebx: int {
+  # data structure
+  var numbers-storage: (array int 0x100)  # 256 ints
+  var numbers/esi: (addr array int) <- address numbers-storage
+  var numbers-index/ecx: int <- copy 0
+  # phase 1: parse each line from stdin and add it to numbers
+  {
+    var line-storage: (stream byte 0x100)  # 256 bytes
+    var line/edx: (addr stream byte) <- address line-storage
+    {
+#?       print-string 0, "== iter\n"
+      # read line from stdin
+      clear-stream line
+      read-line-from-real-keyboard line
+      # if line is empty (not even a newline), quit
+      var done?/eax: boolean <- stream-empty? line
+      compare done?, 0  # false
+      break-if-!=
+#?       print-stream-to-real-screen line
+      # convert line to int and append it to numbers
+      var n/eax: int <- parse-decimal-int-from-stream line
+#?       print-int32-decimal 0, n
+#?       print-string 0, "\n"
+      var dest/ebx: (addr int) <- index numbers, numbers-index
+      copy-to *dest, n
+      numbers-index <- increment
+#?       print-string 0, "== "
+#?       print-int32-decimal 0, numbers-index
+#?       print-string 0, "\n"
+      loop
+    }
+  }
+  # phase 2: construct table of 2-sums
+  var two-sums-storage: (array int 0x10000)  # 256 * 256 ints
+  var two-sums/edi: (addr array int) <- address two-sums-storage
+  var i/eax: int <- copy 0
+  {
+    compare i, numbers-index
+    break-if->=
+    # for j from i+1 to end
+    var j/edx: int <- copy i
+    j <- increment
+    {
+      compare j, numbers-index
+      break-if->=
+      {
+        compare i, j
+        break-if-=
+        var result-index/ebx: int <- copy 0x100
+        result-index <- multiply i
+        result-index <- add j
+        var dest/ebx: (addr int) <- index two-sums, result-index
+        var src/eax: (addr int) <- index numbers, i
+        var result/eax: int <- copy *src
+        var src2/edx: (addr int) <- index numbers, j
+        result <- add *src2
+        copy-to *dest, result
+      }
+      j <- increment
+      loop
+    }
+    i <- increment
+    loop
+  }
+  # phase 3: for each number in two-sums, check if 2020-it is in the rest of
+  # the array
+  return 1  # not found
+}
+
+fn find-after _numbers: (addr array int), start: int, _target: int -> _/eax: boolean {
+  var numbers/esi: (addr array int) <- copy _numbers
+  var target/edi: int <- copy _target
+  var len/ecx: int <- length numbers
+  var i/eax: int <- copy start
+  i <- increment
+  {
+    compare i, len
+    break-if->=
+    var src/edx: (addr int) <- index numbers, i
+    # if *src == target, return true
+    compare *src, target
+    {
+      break-if-!=
+      return 1  # true
+    }
+    i <- increment
+    loop
+  }
+  return 0  # false
+}