tasks a-s

Task/Semordnilap/Go/semordnilap.go

@@ -0,0 +1,58 @@
+package main
+
+import (
+    "fmt"
+    "io/ioutil"
+    "log"
+    "strings"
+)
+
+func main() {
+    // read file into memory as one big block
+    data, err := ioutil.ReadFile("unixdict.txt")
+    if err != nil {
+        log.Fatal(err)
+    }
+    // copy the block, split it up into words
+    words := strings.Split(string(data), "\n")
+    // optional, free the first block for garbage collection
+    data = nil
+    // put words in a map, also determine length of longest word
+    m := make(map[string]bool)
+    longest := 0
+    for _, w := range words {
+        m[string(w)] = true
+        if len(w) > longest {
+            longest = len(w)
+        }
+    }
+    // allocate a buffer for reversing words
+    r := make([]byte, longest)
+    // iterate over word list
+    sem := 0
+    var five []string
+    for _, w := range words {
+        // first, delete from map.  this prevents a palindrome from matching
+        // itself, and also prevents it's reversal from matching later.
+        delete(m, w)
+        // use buffer to reverse word
+        last := len(w) - 1
+        for i := 0; i < len(w); i++ {
+            r[i] = w[last-i]
+        }
+        rs := string(r[:len(w)])
+        // see if reversed word is in map, accumulate results
+        if m[rs] {
+            sem++
+            if len(five) < 5 {
+                five = append(five, w+"/"+rs)
+            }
+        }
+    }
+    // print results
+    fmt.Println(sem, "pairs")
+    fmt.Println("examples:")
+    for _, e := range five {
+        fmt.Println("  ", e)
+    }
+}