Data commit

Task/Untouchable-numbers/Go/untouchable-numbers-1.go

@@ -0,0 +1,113 @@
+package main
+
+import "fmt"
+
+func sumDivisors(n int) int {
+    sum := 1
+    k := 2
+    if n%2 == 0 {
+        k = 1
+    }
+    for i := 1 + k; i*i <= n; i += k {
+        if n%i == 0 {
+            sum += i
+            j := n / i
+            if j != i {
+                sum += j
+            }
+        }
+    }
+    return sum
+}
+
+func sieve(n int) []bool {
+    n++
+    s := make([]bool, n+1) // all false by default
+    for i := 6; i <= n; i++ {
+        sd := sumDivisors(i)
+        if sd <= n {
+            s[sd] = true
+        }
+    }
+    return s
+}
+
+func primeSieve(limit int) []bool {
+    limit++
+    // True denotes composite, false denotes prime.
+    c := make([]bool, limit) // all false by default
+    c[0] = true
+    c[1] = true
+    // no need to bother with even numbers over 2 for this task
+    p := 3 // Start from 3.
+    for {
+        p2 := p * p
+        if p2 >= limit {
+            break
+        }
+        for i := p2; i < limit; i += 2 * p {
+            c[i] = true
+        }
+        for {
+            p += 2
+            if !c[p] {
+                break
+            }
+        }
+    }
+    return c
+}
+
+func commatize(n int) string {
+    s := fmt.Sprintf("%d", n)
+    if n < 0 {
+        s = s[1:]
+    }
+    le := len(s)
+    for i := le - 3; i >= 1; i -= 3 {
+        s = s[0:i] + "," + s[i:]
+    }
+    if n >= 0 {
+        return s
+    }
+    return "-" + s
+}
+
+func main() {
+    limit := 1000000
+    c := primeSieve(limit)
+    s := sieve(63 * limit)
+    untouchable := []int{2, 5}
+    for n := 6; n <= limit; n += 2 {
+        if !s[n] && c[n-1] && c[n-3] {
+            untouchable = append(untouchable, n)
+        }
+    }
+    fmt.Println("List of untouchable numbers <= 2,000:")
+    count := 0
+    for i := 0; untouchable[i] <= 2000; i++ {
+        fmt.Printf("%6s", commatize(untouchable[i]))
+        if (i+1)%10 == 0 {
+            fmt.Println()
+        }
+        count++
+    }
+    fmt.Printf("\n\n%7s untouchable numbers were found  <=     2,000\n", commatize(count))
+    p := 10
+    count = 0
+    for _, n := range untouchable {
+        count++
+        if n > p {
+            cc := commatize(count - 1)
+            cp := commatize(p)
+            fmt.Printf("%7s untouchable numbers were found  <= %9s\n", cc, cp)
+            p = p * 10
+            if p == limit {
+                break
+            }
+        }
+    }
+    cu := commatize(len(untouchable))
+    cl := commatize(limit)
+    fmt.Printf("%7s untouchable numbers were found  <= %s\n", cu, cl)
+}

Task/Untouchable-numbers/Go/untouchable-numbers-2.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+    "fmt"
+    "rcu"
+)
+
+func main() {
+    limit := 1000000
+    m := 63
+    c := rcu.PrimeSieve(limit, false)
+    n := m*limit + 1
+    sumDivs := make([]int, n)
+    for i := 1; i < n; i++ {
+        for j := i; j < n; j += i {
+            sumDivs[j] += i
+        }
+    }
+    s := make([]bool, n) // all false
+    for i := 1; i < n; i++ {
+        sum := sumDivs[i] - i // proper divs sum
+        if sum <= n {
+            s[sum] = true
+        }
+    }
+    untouchable := []int{2, 5}
+    for n := 6; n <= limit; n += 2 {
+        if !s[n] && c[n-1] && c[n-3] {
+            untouchable = append(untouchable, n)
+        }
+    }
+    fmt.Println("List of untouchable numbers <=   2,000:")
+    count := 0
+    for i := 0; untouchable[i] <= 2000; i++ {
+        fmt.Printf("%6s", rcu.Commatize(untouchable[i]))
+        if (i+1)%10 == 0 {
+            fmt.Println()
+        }
+        count++
+    }
+    fmt.Printf("\n\n%7s untouchable numbers were found  <=     2,000\n", rcu.Commatize(count))
+    p := 10
+    count = 0
+    for _, n := range untouchable {
+        count++
+        if n > p {
+            cc := rcu.Commatize(count - 1)
+            cp := rcu.Commatize(p)
+            fmt.Printf("%7s untouchable numbers were found  <= %9s\n", cc, cp)
+            p = p * 10
+            if p == limit {
+                break
+            }
+        }
+    }
+    cu := rcu.Commatize(len(untouchable))
+    cl := rcu.Commatize(limit)
+    fmt.Printf("%7s untouchable numbers were found  <= %s\n", cu, cl)
+}