RosettaCodeData/Task/Knuths-power-tree/Java/knuths-power-tree.java

68 lines
1.9 KiB
Java

import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class PowerTree {
private static Map<Integer, Integer> p = new HashMap<>();
private static List<List<Integer>> lvl = new ArrayList<>();
static {
p.put(1, 0);
ArrayList<Integer> temp = new ArrayList<>();
temp.add(1);
lvl.add(temp);
}
private static List<Integer> path(int n) {
if (n == 0) return new ArrayList<>();
while (!p.containsKey(n)) {
List<Integer> q = new ArrayList<>();
for (Integer x : lvl.get(0)) {
for (Integer y : path(x)) {
if (p.containsKey(x + y)) break;
p.put(x + y, x);
q.add(x + y);
}
}
lvl.get(0).clear();
lvl.get(0).addAll(q);
}
List<Integer> temp = path(p.get(n));
temp.add(n);
return temp;
}
private static BigDecimal treePow(double x, int n) {
Map<Integer, BigDecimal> r = new HashMap<>();
r.put(0, BigDecimal.ONE);
r.put(1, BigDecimal.valueOf(x));
int p = 0;
for (Integer i : path(n)) {
r.put(i, r.get(i - p).multiply(r.get(p)));
p = i;
}
return r.get(n);
}
private static void showPow(double x, int n, boolean isIntegral) {
System.out.printf("%d: %s\n", n, path(n));
String f = isIntegral ? "%.0f" : "%f";
System.out.printf(f, x);
System.out.printf(" ^ %d = ", n);
System.out.printf(f, treePow(x, n));
System.out.println("\n");
}
public static void main(String[] args) {
for (int n = 0; n <= 17; ++n) {
showPow(2.0, n, true);
}
showPow(1.1, 81, false);
showPow(3.0, 191, true);
}
}