tasks a-s

Task/Self-referential-sequence/Go/self-referential-sequence.go

@@ -0,0 +1,75 @@
+package main
+
+import (
+    "fmt"
+    "strconv"
+)
+
+func main() {
+    var maxLen int
+    var seqMaxLen [][]string
+    for n := 1; n < 1e6; n++ {
+        switch s := seq(n); {
+        case len(s) == maxLen:
+            seqMaxLen = append(seqMaxLen, s)
+        case len(s) > maxLen:
+            maxLen = len(s)
+            seqMaxLen = [][]string{s}
+        }
+    }
+    fmt.Println("Max sequence length:", maxLen)
+    fmt.Println("Sequences:", len(seqMaxLen))
+    for _, seq := range seqMaxLen {
+        fmt.Println("Sequence:")
+        for _, t := range seq {
+            fmt.Println(t)
+        }
+    }
+}
+
+func seq(n int) []string {
+    s := strconv.Itoa(n)
+    ss := []string{s}
+
+    for {
+        dSeq := sortD(s)
+        d := dSeq[0]
+        nd := 1
+        s = ""
+        for i := 1; ; i++ {
+            if i == len(dSeq) {
+                s = fmt.Sprintf("%s%d%c", s, nd, d)
+                break
+            }
+            if dSeq[i] == d {
+                nd++
+            } else {
+                s = fmt.Sprintf("%s%d%c", s, nd, d)
+                d = dSeq[i]
+                nd = 1
+            }
+        }
+        for _, s0 := range ss {
+            if s == s0 {
+                return ss
+            }
+        }
+        ss = append(ss, s)
+    }
+    panic("unreachable")
+}
+
+func sortD(s string) []rune {
+    r := make([]rune, len(s))
+    for i, d := range s {
+        j := 0
+        for ; j < i; j++ {
+            if d > r[j] {
+                copy(r[j+1:], r[j:i])
+                break
+            }
+        }
+        r[j] = d
+    }
+    return r
+}