Permutation.java

/**
 * Permutation.java
 *
 * Copyright 2016 the original author or authors.
 *
 * We licenses this file to you under the Apache License, version 2.0
 * (the "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at:
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package org.apache.niolex.common.algorithm;


/**
 * @author <a href="mailto:xiejiyun@foxmail.com">Xie, Jiyun</a>
 * @version 1.0.0
 * @since 2016-3-28
 */
public class Permutation {

    public static void print(char[] a) {
        System.out.println(a);
    }

    public static void swap(char[] a, int i, int j) {
        char c = a[i];
        a[i] = a[j];
        a[j] = c;
    }

    public static void permute(char[] a, int curp) {
        if (curp == a.length - 1) {
            print(a);
        } else {
            permute(a, curp + 1);
            for (int k = curp + 1; k < a.length; ++k) {
                swap(a, curp, k);
                permute(a, curp + 1);
                swap(a, k, curp);
            }
        }
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        String s = "abcd";
        permute(s.toCharArray(), 0);
    }

}