Method set11Perm

app/src/main/java/solver/Utils.java:64–76

(int[] arr, int idx, int len)

    }

    static void set11Perm(int[] arr, int idx, int len) {
        long val = 0xa9876543210L;
        for (int i = 0; i < len - 1; i++) {
            int p = fact[len - 1 - i];
            int v = idx / p;
            idx -= v * p;
            v <<= 2;
            arr[i] = (int) ((val >> v) & 0xf);
            long m = (1L << v) - 1;
            val = (val & m) + ((val >> 4) & ~m);
        }
        arr[len - 1] = (int) (val & 0xf);
    }

    static int get11Perm(int[] arr, int len) {
        int idx = 0;