Data commit

Task/Multi-base-primes/Go/multi-base-primes.go

@@ -0,0 +1,97 @@
+package main
+
+import (
+    "fmt"
+    "math"
+    "rcu"
+)
+
+var maxDepth = 6
+var maxBase = 36
+var c = rcu.PrimeSieve(int(math.Pow(float64(maxBase), float64(maxDepth))), true)
+var digits = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+var maxStrings [][][]int
+var mostBases = -1
+
+func maxSlice(a []int) int {
+    max := 0
+    for _, e := range a {
+        if e > max {
+            max = e
+        }
+    }
+    return max
+}
+
+func maxInt(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+
+func process(indices []int) {
+    minBase := maxInt(2, maxSlice(indices)+1)
+    if maxBase - minBase + 1 < mostBases {
+        return  // can't affect results so return
+    }
+    var bases []int
+    for b := minBase; b <= maxBase; b++ {
+        n := 0
+        for _, i := range indices {
+            n = n*b + i
+        }
+        if !c[n] {
+            bases = append(bases, b)
+        }
+    }
+    count := len(bases)
+    if count > mostBases {
+        mostBases = count
+        indices2 := make([]int, len(indices))
+        copy(indices2, indices)
+        maxStrings = [][][]int{[][]int{indices2, bases}}
+    } else if count == mostBases {
+        indices2 := make([]int, len(indices))
+        copy(indices2, indices)
+        maxStrings = append(maxStrings, [][]int{indices2, bases})
+    }
+}
+
+func printResults() {
+    fmt.Printf("%d\n", len(maxStrings[0][1]))
+    for _, m := range maxStrings {
+        s := ""
+        for _, i := range m[0] {
+            s = s + string(digits[i])
+        }
+        fmt.Printf("%s -> %v\n", s, m[1])
+    }
+}
+
+func nestedFor(indices []int, length, level int) {
+    if level == len(indices) {
+        process(indices)
+    } else {
+        indices[level] = 0
+        if level == 0 {
+            indices[level] = 1
+        }
+        for indices[level] < length {
+            nestedFor(indices, length, level+1)
+            indices[level]++
+        }
+    }
+}
+
+func main() {
+    for depth := 1; depth <= maxDepth; depth++ {
+        fmt.Print(depth, " character strings which are prime in most bases: ")
+        maxStrings = maxStrings[:0]
+        mostBases = -1
+        indices := make([]int, depth)
+        nestedFor(indices, maxBase, 0)
+        printResults()
+        fmt.Println()
+    }
+}