Data commit

Task/Padovan-sequence/Go/padovan-sequence.go

@@ -0,0 +1,106 @@
+package main
+
+import (
+    "fmt"
+    "math"
+    "math/big"
+    "strings"
+)
+
+func padovanRecur(n int) []int {
+    p := make([]int, n)
+    p[0], p[1], p[2] = 1, 1, 1
+    for i := 3; i < n; i++ {
+        p[i] = p[i-2] + p[i-3]
+    }
+    return p
+}
+
+func padovanFloor(n int) []int {
+    var p, s, t, u = new(big.Rat), new(big.Rat), new(big.Rat), new(big.Rat)
+    p, _ = p.SetString("1.324717957244746025960908854")
+    s, _ = s.SetString("1.0453567932525329623")
+    f := make([]int, n)
+    pow := new(big.Rat).SetInt64(1)
+    u = u.SetFrac64(1, 2)
+    t.Quo(pow, p)
+    t.Quo(t, s)
+    t.Add(t, u)
+    v, _ := t.Float64()
+    f[0] = int(math.Floor(v))
+    for i := 1; i < n; i++ {
+        t.Quo(pow, s)
+        t.Add(t, u)
+        v, _ = t.Float64()
+        f[i] = int(math.Floor(v))
+        pow.Mul(pow, p)
+    }
+    return f
+}
+
+type LSystem struct {
+    rules         map[string]string
+    init, current string
+}
+
+func step(lsys *LSystem) string {
+    var sb strings.Builder
+    if lsys.current == "" {
+        lsys.current = lsys.init
+    } else {
+        for _, c := range lsys.current {
+            sb.WriteString(lsys.rules[string(c)])
+        }
+        lsys.current = sb.String()
+    }
+    return lsys.current
+}
+
+func padovanLSys(n int) []string {
+    rules := map[string]string{"A": "B", "B": "C", "C": "AB"}
+    lsys := &LSystem{rules, "A", ""}
+    p := make([]string, n)
+    for i := 0; i < n; i++ {
+        p[i] = step(lsys)
+    }
+    return p
+}
+
+// assumes lists are same length
+func areSame(l1, l2 []int) bool {
+    for i := 0; i < len(l1); i++ {
+        if l1[i] != l2[i] {
+            return false
+        }
+    }
+    return true
+}
+
+func main() {
+    fmt.Println("First 20 members of the Padovan sequence:")
+    fmt.Println(padovanRecur(20))
+    recur := padovanRecur(64)
+    floor := padovanFloor(64)
+    same := areSame(recur, floor)
+    s := "give"
+    if !same {
+        s = "do not give"
+    }
+    fmt.Println("\nThe recurrence and floor based functions", s, "the same results for 64 terms.")
+
+    p := padovanLSys(32)
+    lsyst := make([]int, 32)
+    for i := 0; i < 32; i++ {
+        lsyst[i] = len(p[i])
+    }
+    fmt.Println("\nFirst 10 members of the Padovan L-System:")
+    fmt.Println(p[:10])
+    fmt.Println("\nand their lengths:")
+    fmt.Println(lsyst[:10])
+
+    same = areSame(recur[:32], lsyst)
+    s = "give"
+    if !same {
+        s = "do not give"
+    }
+    fmt.Println("\nThe recurrence and L-system based functions", s, "the same results for 32 terms.")