Data commit

Task/Humble-numbers/Go/humble-numbers.go

@@ -0,0 +1,95 @@
+package main
+
+import (
+    "fmt"
+    "math/big"
+)
+
+var (
+    one   = new(big.Int).SetUint64(1)
+    two   = new(big.Int).SetUint64(2)
+    three = new(big.Int).SetUint64(3)
+    five  = new(big.Int).SetUint64(5)
+    seven = new(big.Int).SetUint64(7)
+    ten   = new(big.Int).SetUint64(10)
+)
+
+func min(a, b *big.Int) *big.Int {
+    if a.Cmp(b) < 0 {
+        return a
+    }
+    return b
+}
+
+func humble(n int) []*big.Int {
+    h := make([]*big.Int, n)
+    h[0] = new(big.Int).Set(one)
+    next2, next3 := new(big.Int).Set(two), new(big.Int).Set(three)
+    next5, next7 := new(big.Int).Set(five), new(big.Int).Set(seven)
+    var i, j, k, l int
+    for m := 1; m < len(h); m++ {
+        h[m] = new(big.Int).Set(min(next2, min(next3, min(next5, next7))))
+        if h[m].Cmp(next2) == 0 {
+            i++
+            next2.Mul(two, h[i])
+        }
+        if h[m].Cmp(next3) == 0 {
+            j++
+            next3.Mul(three, h[j])
+        }
+        if h[m].Cmp(next5) == 0 {
+            k++
+            next5.Mul(five, h[k])
+        }
+        if h[m].Cmp(next7) == 0 {
+            l++
+            next7.Mul(seven, h[l])
+        }
+    }
+    return h
+}
+
+func commatize(n int) string {
+    s := fmt.Sprintf("%d", n)
+    le := len(s)
+    for i := le - 3; i >= 1; i -= 3 {
+        s = s[0:i] + "," + s[i:]
+    }
+    return s
+}
+
+func main() {
+    const n = 13 * 1e6  // calculate the first 13 million humble numbers, say
+    h := humble(n)
+    fmt.Println("The first 50 humble numbers are:")
+    fmt.Println(h[0:50])
+
+    maxDigits := len(h[len(h)-1].String()) - 1
+    counts := make([]int, maxDigits+1)
+    var maxUsed int
+    digits := 1
+    pow10 := new(big.Int).Set(ten)
+    for i := 0; i < len(h); i++ {
+        for {
+            if h[i].Cmp(pow10) >= 0 {
+                pow10.Mul(pow10, ten)
+                digits++
+            } else {
+                break
+            }
+        }
+        if digits > maxDigits {
+            maxUsed = i
+            break
+        }
+        counts[digits]++
+    }
+    fmt.Printf("\nOf the first %s humble numbers:\n", commatize(maxUsed))
+    for i := 1; i <= maxDigits; i++ {
+        s := "s"
+        if i == 1 {
+            s = ""
+        }
+        fmt.Printf("%9s have %2d digit%s\n", commatize(counts[i]), i, s)
+    }
+}