Data commit

Task/Taxicab-numbers/Java/taxicab-numbers.java

@@ -0,0 +1,75 @@
+import java.util.PriorityQueue;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Iterator;
+
+class CubeSum implements Comparable<CubeSum> {
+	public long x, y, value;
+
+	public CubeSum(long x, long y) {
+		this.x = x;
+		this.y = y;
+		this.value = x*x*x + y*y*y;
+	}
+
+	public String toString() {
+		return String.format("%4d^3 + %4d^3", x, y);
+	}
+
+	public int compareTo(CubeSum that) {
+		return value < that.value ? -1 : value > that.value ? 1 : 0;
+	}
+}
+
+class SumIterator implements Iterator<CubeSum> {
+	PriorityQueue<CubeSum> pq = new PriorityQueue<CubeSum>();
+	long n = 0;
+
+	public boolean hasNext() { return true; }
+	public CubeSum next() {
+		while (pq.size() == 0 || pq.peek().value >= n*n*n)
+			pq.add(new CubeSum(++n, 1));
+
+		CubeSum s = pq.remove();
+		if (s.x > s.y + 1) pq.add(new CubeSum(s.x, s.y+1));
+
+		return s;
+	}
+}
+
+class TaxiIterator implements Iterator<List<CubeSum>> {
+	Iterator<CubeSum> sumIterator = new SumIterator();
+	CubeSum last = sumIterator.next();
+
+	public boolean hasNext() { return true; }
+	public List<CubeSum> next() {
+		CubeSum s;
+		List<CubeSum> train = new ArrayList<CubeSum>();
+
+		while ((s = sumIterator.next()).value != last.value)
+			last = s;
+
+		train.add(last);
+
+		do { train.add(s); } while ((s = sumIterator.next()).value == last.value);
+		last = s;
+
+		return train;
+	}
+}
+	
+public class Taxi {
+	public static final void main(String[] args) {
+		Iterator<List<CubeSum>> taxi = new TaxiIterator();
+
+		for (int i = 1; i <= 2006; i++) {
+			List<CubeSum> t = taxi.next();
+			if (i > 25 && i < 2000) continue;
+
+			System.out.printf("%4d: %10d", i, t.get(0).value);
+			for (CubeSum s: t)
+				System.out.print(" = " + s);
+			System.out.println();
+		}
+	}
+}