Java String Permutation nextPermutation(String f)

Description

Create next permutation based on provided.

License

Apache License

Return

next permutation.

Declaration

public static String nextPermutation(String f) 

Method Source Code

//package com.java2s;
//License from project: Apache License 

public class Main {
    /**/*  ww  w .java  2  s  . com*/
     * Create next permutation based on provided. a -> b <br/>
     * z -> aa <br/>
     * aa -> ab <br/>
     * az -> ba <br/>
     * bz -> ca <br/>
     * zz -> aaa <br/>
     * 
     * @return next permutation.
     */
    public static String nextPermutation(String f) {
        boolean onlyZ = true;
        for (int i = 0; i < f.length(); ++i)
            if (f.charAt(i) != 'z')
                onlyZ = false;
        if (onlyZ) {
            String s = "";
            for (int i = 0; i <= f.length(); ++i)
                s = s + 'a';
            return s;
        }
        for (int i = f.length() - 1; i > -1; --i)
            if (f.charAt(i) != 'z') {
                if (i == f.length() - 1) {
                    char last = (char) (f.charAt(i) + 1);
                    return f.substring(0, f.length() - 1) + new Character(last).toString();
                } else {
                    char symb = (char) (f.charAt(i) + 1);
                    String postfix = "";
                    for (int u = i + 1; u < f.length(); ++u) {
                        postfix += "a";
                    }
                    return f.substring(0, i) + new Character(symb).toString() + postfix;
                }
            }
        return f;
    }
}