All Permutations of String

Question: Generate all permutations of a given string.

Solution:

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private List<String> permutations = new ArrayList<String>();           /**      *  Generate all the  permutations and add to array list      *       * @param in      * @param out      * @param used      * @param len      * @param recLen      */     void permute(char[] in, char[] out, char[] used, int len, int recLen)     {               if(recLen==len) {             permutations.add(String.valueOf(out));              return;         }               for(int i=0; i<len; i++) {             if(used[i]==1) {                 continue;             }             out[recLen]=in[i];             used[i]=1;             permute(in, out, used, len, recLen+1);             used[i]=0;         }           }           List<String> permutations(String num)     {         char[] out = new char[num.length()];         char[] used = new char[num.length()];               permute(num.toCharArray(), out, used, num.length(), 0);         return permutations;     }