Data commit

Task/Pancake-numbers/D/pancake-numbers.d

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+import std.stdio;
+import std.algorithm;
+import std.random;
+import std.range;
+
+int pancake(int n) {
+    int gap = 2, sum = 2, adj = -1;
+	
+    while (sum < n) {
+        adj++;
+        gap = 2 * gap - 1;
+        sum += gap;
+    }
+	
+    return n + adj;
+}
+
+Range pancakeSort(Range)(Range r) {
+	foreach_reverse (immutable i; 2 .. r.length + 1) {
+		immutable maxIndex = i - r[0 .. i].minPos!q{a > b}.length;
+		
+		if (maxIndex + 1 != i) {
+			if (maxIndex != 0) {
+				r[0 .. maxIndex + 1].reverse();
+			}
+			
+			r[0 .. i].reverse();
+		}
+	}
+	
+	return r;
+}
+
+void main() {
+	writeln("\nThe maximum number of flips to sort a given number of elements is:\n");
+	
+	foreach (i; 1..11)
+	{
+		auto data = iota(1, i+1).array;
+		
+		if (i != 1) {
+			// Protection against the edge case data.lenght == 1 not handled by randomShuffle
+			// where also data is invariant with regard to pancakeSort
+			do
+				data.randomShuffle;
+			while (data.isSorted);
+		}
+		
+		auto sortedData = data.dup;
+		sortedData.pancakeSort;
+		
+		writefln("pancake(%2d) = %2d  e.g  %s  ->  %s", i, pancake(i), data, sortedData);
+	}
+}