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copied!<p>You want this:</p> <pre><code>/************************************************************************* * Compilation: javac Permutations.java * Execution: java Permutations N * * Enumerates all permutations on N elements. * Two different approaches are included. * * % java Permutations 3 * abc * acb * bac * bca * cab * cba * *************************************************************************/ public class Permutations { // print N! permutation of the characters of the string s (in order) public static void perm1(String s) { perm1("", s); } private static void perm1(String prefix, String s) { int N = s.length(); if (N == 0) System.out.println(prefix); else { for (int i = 0; i < N; i++) perm1(prefix + s.charAt(i), s.substring(0, i) + s.substring(i+1, N)); } } // print N! permutation of the elements of array a (not in order) public static void perm2(String s) { int N = s.length(); char[] a = new char[N]; for (int i = 0; i < N; i++) a[i] = s.charAt(i); perm2(a, N); } private static void perm2(char[] a, int n) { if (n == 1) { System.out.println(a); return; } for (int i = 0; i < n; i++) { swap(a, i, n-1); perm2(a, n-1); swap(a, i, n-1); } } // swap the characters at indices i and j private static void swap(char[] a, int i, int j) { char c; c = a[i]; a[i] = a[j]; a[j] = c; } public static void main(String[] args) { int N = Integer.parseInt(args[0]); String alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; String elements = alphabet.substring(0, N); perm1(elements); System.out.println(); perm2(elements); } } </code></pre>

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