algorithm/permutationStr/src/Permutations.java at master · wodgithub/algorithm · GitHub

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import java.util.Scanner;

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) {

// System.out.println("prefix: " + prefix);

// System.out.println("s: " + 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()-1;

char[] a = new char[N];

for (int i = 0; i < N; i++)

a[i] = s.charAt(i);

char[] a = s.toCharArray();

perm2(a, N);

}

private static void perm2(char[] a, int n) {

if (n == 0) {

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 tmp = a[i];

a[i] = a[j];

a[j] = tmp;

}

public static void main(String[] args) {

Scanner s = new Scanner(System.in);

System.out.println("enter the number: ");

int N = Integer.parseInt(s.nextLine());

String alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

String elements = alphabet.substring(0, N);

perm1(elements);

System.out.println();

perm2(elements);

}

algorithm/permutationStr/src/Permutations.java at master · wodgithub/algorithm · GitHub

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