Data commit

Task/Minimal-steps-down-to-1/Go/minimal-steps-down-to-1.go

@@ -0,0 +1,94 @@
+package main
+
+import (
+    "fmt"
+    "strings"
+)
+
+const limit = 50000
+
+var (
+    divs, subs []int
+    mins       [][]string
+)
+
+// Assumes the numbers are presented in order up to 'limit'.
+func minsteps(n int) {
+    if n == 1 {
+        mins[1] = []string{}
+        return
+    }
+    min := limit
+    var p, q int
+    var op byte
+    for _, div := range divs {
+        if n%div == 0 {
+            d := n / div
+            steps := len(mins[d]) + 1
+            if steps < min {
+                min = steps
+                p, q, op = d, div, '/'
+            }
+        }
+    }
+    for _, sub := range subs {
+        if d := n - sub; d >= 1 {
+            steps := len(mins[d]) + 1
+            if steps < min {
+                min = steps
+                p, q, op = d, sub, '-'
+            }
+        }
+    }
+    mins[n] = append(mins[n], fmt.Sprintf("%c%d -> %d", op, q, p))
+    mins[n] = append(mins[n], mins[p]...)
+}
+
+func main() {
+    for r := 0; r < 2; r++ {
+        divs = []int{2, 3}
+        if r == 0 {
+            subs = []int{1}
+        } else {
+            subs = []int{2}
+        }
+        mins = make([][]string, limit+1)
+        fmt.Printf("With: Divisors: %v, Subtractors: %v =>\n", divs, subs)
+        fmt.Println("  Minimum number of steps to diminish the following numbers down to 1 is:")
+        for i := 1; i <= limit; i++ {
+            minsteps(i)
+            if i <= 10 {
+                steps := len(mins[i])
+                plural := "s"
+                if steps == 1 {
+                    plural = " "
+                }
+                fmt.Printf("    %2d: %d step%s: %s\n", i, steps, plural, strings.Join(mins[i], ", "))
+            }
+        }
+        for _, lim := range []int{2000, 20000, 50000} {
+            max := 0
+            for _, min := range mins[0 : lim+1] {
+                m := len(min)
+                if m > max {
+                    max = m
+                }
+            }
+            var maxs []int
+            for i, min := range mins[0 : lim+1] {
+                if len(min) == max {
+                    maxs = append(maxs, i)
+                }
+            }
+            nums := len(maxs)
+            verb, verb2, plural := "are", "have", "s"
+            if nums == 1 {
+                verb, verb2, plural = "is", "has", ""
+            }
+            fmt.Printf("  There %s %d number%s in the range 1-%d ", verb, nums, plural, lim)
+            fmt.Printf("that %s maximum 'minimal steps' of %d:\n", verb2, max)
+            fmt.Println("   ", maxs)
+        }
+        fmt.Println()
+    }
+}