Data commit

Task/Magnanimous-numbers/Go/magnanimous-numbers.go

@@ -0,0 +1,90 @@
+package main
+
+import "fmt"
+
+// OK for 'small' numbers.
+func isPrime(n uint64) bool {
+    switch {
+    case n < 2:
+        return false
+    case n%2 == 0:
+        return n == 2
+    case n%3 == 0:
+        return n == 3
+    default:
+        d := uint64(5)
+        for d*d <= n {
+            if n%d == 0 {
+                return false
+            }
+            d += 2
+            if n%d == 0 {
+                return false
+            }
+            d += 4
+        }
+        return true
+    }
+}
+
+func ord(n int) string {
+    m := n % 100
+    if m >= 4 && m <= 20 {
+        return fmt.Sprintf("%dth", n)
+    }
+    m %= 10
+    suffix := "th"
+    if m < 4 {
+        switch m {
+        case 1:
+            suffix = "st"
+        case 2:
+            suffix = "nd"
+        case 3:
+            suffix = "rd"
+        }
+    }
+    return fmt.Sprintf("%d%s", n, suffix)
+}
+
+func isMagnanimous(n uint64) bool {
+    if n < 10 {
+        return true
+    }
+    for p := uint64(10); ; p *= 10 {
+        q := n / p
+        r := n % p
+        if !isPrime(q + r) {
+            return false
+        }
+        if q < 10 {
+            break
+        }
+    }
+    return true
+}
+
+func listMags(from, thru, digs, perLine int) {
+    if from < 2 {
+        fmt.Println("\nFirst", thru, "magnanimous numbers:")
+    } else {
+        fmt.Printf("\n%s through %s magnanimous numbers:\n", ord(from), ord(thru))
+    }
+    for i, c := uint64(0), 0; c < thru; i++ {
+        if isMagnanimous(i) {
+            c++
+            if c >= from {
+                fmt.Printf("%*d ", digs, i)
+                if c%perLine == 0 {
+                    fmt.Println()
+                }
+            }
+        }
+    }
+}
+
+func main() {
+    listMags(1, 45, 3, 15)
+    listMags(241, 250, 1, 10)
+    listMags(391, 400, 1, 10)
+}