A-M baby

Task/Knapsack-problem-Continuous/D/knapsack-problem-continuous-1.d

@@ -0,0 +1,49 @@
+import std.stdio, std.algorithm, std.string, std.conv;
+
+struct Item {
+    string name;
+    real amount, value;
+
+    @property real valuePerKG() const pure nothrow {
+        return value / amount;
+    }
+
+    string toString() const /*pure nothrow*/ {
+        return format("%10s %7.2f %7.2f %7.2f",
+                      name, amount, value, valuePerKG);
+    }
+}
+
+real sum(string field)(in Item[] items) pure nothrow {
+    return reduce!("a + b." ~ field)(0.0L, items);
+}
+
+void main() {
+    Item[] raw = [{"beef",    3.8, 36.0},
+                  {"pork",    5.4, 43.0},
+                  {"ham",     3.6, 90.0},
+                  {"greaves", 2.4, 45.0},
+                  {"flitch",  4.0, 30.0},
+                  {"brawn",   2.5, 56.0},
+                  {"welt",    3.7, 67.0},
+                  {"salami",  3.0, 95.0},
+                  {"sausage", 5.9, 98.0}];
+
+    // reverse sorted by Value per amount
+    const items = raw.sort!q{a.valuePerKG > b.valuePerKG}().release();
+
+    const(Item)[] chosen;
+    real space = 15.0;
+    foreach (item; items)
+        if (item.amount < space) {
+            chosen ~= item;
+            space -= item.amount;
+        } else {
+            chosen ~= Item(item.name, space, item.valuePerKG * space);
+            break;
+        }
+
+    writefln("%10s %7s %7s %7s", "ITEM", "AMOUNT", "VALUE", "$/unit");
+    writefln("%(%s\n%)", chosen);
+    writeln(Item("TOTAL", sum!"amount"(chosen), sum!"value"(chosen)));
+}