Data commit

Task/Weird-numbers/Go/weird-numbers.go

@@ -0,0 +1,78 @@
+package main
+
+import "fmt"
+
+func divisors(n int) []int {
+    divs := []int{1}
+    divs2 := []int{}
+    for i := 2; i*i <= n; i++ {
+        if n%i == 0 {
+            j := n / i
+            divs = append(divs, i)
+            if i != j {
+                divs2 = append(divs2, j)
+            }
+        }
+    }
+    for i := len(divs) - 1; i >= 0; i-- {
+        divs2 = append(divs2, divs[i])
+    }
+    return divs2
+}
+
+func abundant(n int, divs []int) bool {
+    sum := 0
+    for _, div := range divs {
+        sum += div
+    }
+    return sum > n
+}
+
+func semiperfect(n int, divs []int) bool {
+    le := len(divs)
+    if le > 0 {
+        h := divs[0]
+        t := divs[1:]
+        if n < h {
+            return semiperfect(n, t)
+        } else {
+            return n == h || semiperfect(n-h, t) || semiperfect(n, t)
+        }
+    } else {
+        return false
+    }
+}
+
+func sieve(limit int) []bool {
+    // false denotes abundant and not semi-perfect.
+    // Only interested in even numbers >= 2
+    w := make([]bool, limit)
+    for i := 2; i < limit; i += 2 {
+        if w[i] {
+            continue
+        }
+        divs := divisors(i)
+        if !abundant(i, divs) {
+            w[i] = true
+        } else if semiperfect(i, divs) {
+            for j := i; j < limit; j += i {
+                w[j] = true
+            }
+        }
+    }
+    return w
+}
+
+func main() {
+    w := sieve(17000)
+    count := 0
+    const max = 25
+    fmt.Println("The first 25 weird numbers are:")
+    for n := 2; count < max; n += 2 {
+        if !w[n] {
+            fmt.Printf("%d ", n)
+            count++
+        }
+    }
+    fmt.Println()
+}