Data commit

Task/UPC/Go/upc.go

@@ -0,0 +1,126 @@
+package main
+
+import (
+    "fmt"
+    "regexp"
+)
+
+var bits = []string{
+    "0 0 0 1 1 0 1 ",
+    "0 0 1 1 0 0 1 ",
+    "0 0 1 0 0 1 1 ",
+    "0 1 1 1 1 0 1 ",
+    "0 1 0 0 0 1 1 ",
+    "0 1 1 0 0 0 1 ",
+    "0 1 0 1 1 1 1 ",
+    "0 1 1 1 0 1 1 ",
+    "0 1 1 0 1 1 1 ",
+    "0 0 0 1 0 1 1 ",
+}
+
+var (
+    lhs = make(map[string]int)
+    rhs = make(map[string]int)
+)
+
+var weights = []int{3, 1, 3, 1, 3, 1, 3, 1, 3, 1, 3, 1}
+
+const (
+    s = "# #"
+    m = " # # "
+    e = "# #"
+    d = "(?:#| ){7}"
+)
+
+func init() {
+    for i := 0; i <= 9; i++ {
+        lt := make([]byte, 7)
+        rt := make([]byte, 7)
+        for j := 0; j < 14; j += 2 {
+            if bits[i][j] == '1' {
+                lt[j/2] = '#'
+                rt[j/2] = ' '
+            } else {
+                lt[j/2] = ' '
+                rt[j/2] = '#'
+            }
+        }
+        lhs[string(lt)] = i
+        rhs[string(rt)] = i
+    }
+}
+
+func reverse(s string) string {
+    b := []byte(s)
+    for i, j := 0, len(b)-1; i < j; i, j = i+1, j-1 {
+        b[i], b[j] = b[j], b[i]
+    }
+    return string(b)
+}
+
+func main() {
+    barcodes := []string{
+        "         # #   # ##  #  ## #   ## ### ## ### ## #### # # # ## ##  #   #  ##  ## ###  # ##  ## ### #  # #       ",
+        "        # # #   ##   ## # #### #   # ## #   ## #   ## # # # ###  # ###  ##  ## ###  # #  ### ###  # # #         ",
+        "         # #    # # #  ###  #   #    # #  #   #    # # # # ## #   ## #   ## #   ##   # # #### ### ## # #         ",
+        "       # # ##  ## ##  ##   #  #   #  # ###  # ##  ## # # #   ## ##  #  ### ## ## #   # #### ## #   # #        ",
+        "         # # ### ## #   ## ## ###  ##  # ##   #   # ## # # ### #  ## ##  #    # ### #  ## ##  #      # #          ",
+        "          # #  #   # ##  ##  #   #   #  # ##  ##  #   # # # # #### #  ##  # #### #### # #  ##  # #### # #         ",
+        "         # #  #  ##  ##  # #   ## ##   # ### ## ##   # # # #  #   #   #  #  ### # #    ###  # #  #   # #        ",
+        "        # # #    # ##  ##   #  # ##  ##  ### #   #  # # # ### ## ## ### ## ### ### ## #  ##  ### ## # #         ",
+        "         # # ### ##   ## # # #### #   ## # #### # #### # # #   #  # ###  #    # ###  # #    # ###  # # #       ",
+        "        # # # #### ##   # #### # #   ## ## ### #### # # # #  ### # ###  ###  # # ###  #    # #  ### # #         ",
+    }
+
+    // Regular expression to check validity of a barcode and extract digits. However we accept any number
+    // of spaces at the beginning or end i.e. we don't enforce a minimum of 9.
+    expr := fmt.Sprintf(`^\s*%s(%s)(%s)(%s)(%s)(%s)(%s)%s(%s)(%s)(%s)(%s)(%s)(%s)%s\s*$`,
+        s, d, d, d, d, d, d, m, d, d, d, d, d, d, e)
+    rx := regexp.MustCompile(expr)
+    fmt.Println("UPC-A barcodes:")
+    for i, bc := range barcodes {
+        for j := 0; j <= 1; j++ {
+            if !rx.MatchString(bc) {
+                fmt.Printf("%2d: Invalid format\n", i+1)
+                break
+            }
+            codes := rx.FindStringSubmatch(bc)
+            digits := make([]int, 12)
+            var invalid, ok bool // False by default.
+            for i := 1; i <= 6; i++ {
+                digits[i-1], ok = lhs[codes[i]]
+                if !ok {
+                    invalid = true
+                }
+                digits[i+5], ok = rhs[codes[i+6]]
+                if !ok {
+                    invalid = true
+                }
+            }
+            if invalid { // Contains at least one invalid digit.
+                if j == 0 { // Try reversing.
+                    bc = reverse(bc)
+                    continue
+                } else {
+                    fmt.Printf("%2d: Invalid digit(s)\n", i+1)
+                    break
+                }
+            }
+            sum := 0
+            for i, d := range digits {
+                sum += weights[i] * d
+            }
+            if sum%10 != 0 {
+                fmt.Printf("%2d: Checksum error\n", i+1)
+                break
+            } else {
+                ud := ""
+                if j == 1 {
+                    ud = "(upside down)"
+                }
+                fmt.Printf("%2d: %v %s\n", i+1, digits, ud)
+                break
+            }
+        }
+    }
+}