设一组数p = {r1, r2, r3, … ,rn}, 全排列为perm(p)，pn = p - {rn}。
因此perm(p) = r1perm(p1), r2perm(p2), r3perm(p3), … , rnperm(pn)。当n = 1时perm(p} = r1。
实现java代码如下：
public class Permutate {
public static int total = 0;
public static void swap(String[] str, int i, int j)
{
String temp = new String();
temp = str[i];
str[i] = str[j];
str[j] = temp;
}
public static void arrange (String[] str, int st, int len)
{
if (st == len - 1)
{
for (int i = 0; i < len; i ++)
{
System.out.print(str[i]+ " ");
}
System.out.println();
total++;
}
else
{
for (int i = st; i < len; i ++)
{
swap(str, st, i);
arrange(str, st + 1, len);
swap(str, st, i);
}
}
}
/**
* @param args
*/
public static void main(String[] args) {
String str[] = {"a", "b", "c", "d", "e"};
arrange(str, 0, str.length);
System.out.println(total);
}
}