Data commit

Task/Permutations-by-swapping/Java/permutations-by-swapping.java

@@ -0,0 +1,68 @@
+package org.rosettacode.java;
+
+import java.util.Arrays;
+import java.util.stream.IntStream;
+
+public class HeapsAlgorithm {
+
+	public static void main(String[] args) {
+		Object[] array = IntStream.range(0, 4)
+				.boxed()
+				.toArray();
+		HeapsAlgorithm algorithm = new HeapsAlgorithm();
+		algorithm.recursive(array);
+		System.out.println();
+		algorithm.loop(array);
+	}
+
+	void recursive(Object[] array) {
+		recursive(array, array.length, true);
+	}
+
+	void recursive(Object[] array, int n, boolean plus) {
+		if (n == 1) {
+			output(array, plus);
+		} else {
+			for (int i = 0; i < n; i++) {
+				recursive(array, n - 1, i == 0);
+				swap(array, n % 2 == 0 ? i : 0, n - 1);
+			}
+		}
+	}
+
+	void output(Object[] array, boolean plus) {
+		System.out.println(Arrays.toString(array) + (plus ? " +1" : " -1"));
+	}
+
+	void swap(Object[] array, int a, int b) {
+		Object o = array[a];
+		array[a] = array[b];
+		array[b] = o;
+	}
+
+	void loop(Object[] array) {
+		loop(array, array.length);
+	}
+
+	void loop(Object[] array, int n) {
+		int[] c = new int[n];
+		output(array, true);
+		boolean plus = false;
+		for (int i = 0; i < n; ) {
+			if (c[i] < i) {
+				if (i % 2 == 0) {
+					swap(array, 0, i);
+				} else {
+					swap(array, c[i], i);
+				}
+				output(array, plus);
+				plus = !plus;
+				c[i]++;
+				i = 0;
+			} else {
+				c[i] = 0;
+				i++;
+			}
+		}
+	}
+}