Generating all permutation of a character array

Question

After reading so many post of \"generating permutation of string\", I tried to write it in Java. 1) Take the first character start swapping with rest of the character in the

Answer 1

The general idea of your permutation algorithm is correct, but you forgot to handle some of possible cases there.

First. You should add printPermutation(a, i + 1) before going into loop.

Second. Call printPermutation(a, i + 1) instead of printPermutation(a, x) in the loop.

public static void main(String[] args) {
    char a[]= "1234".toCharArray();
    printPermutation(a, 0);
}

private static void printPermutation(char[] a, int i) {
    if (i == a.length - 1) System.out.println(new String(a));
    else {
        printPermutation(a, i + 1);
        for (int x = i + 1; x < a.length; x++) {
            swap(a, i, x);
            printPermutation(a, i + 1);
            reswap(a, i, x);
        }
    }
}

private static void swap(char[] a, int i, int x) {
    char tmp = a[i];
    a[i] = a[x];
    a[x] = tmp;
}

private static void reswap(char[] a, int i, int x) {
    swap(a, i, x);
}