經常會遇到字符串全排列的問題。例如：輸入為{‘a’,’b’,’c’}，則其全排列組合為abc,acb,bac,bca,cba,cab。對於輸入長度為n的字符串數組，全排列組合為n!種。
package Bayes;
public class RecursionTree {
public static void permutation(char[] s,int from,int to) {
if(to<=1)
{
return;
}
if(from ==to)
{
System.out.println(s);
}
else
{
for (int i = from; i <=to; i++) {
swap(s, i, from);
permutation(s, from+1, to);
swap(s, from, i);
}
}
}
public static void swap(char[] s,int i,int j) {
char tmp = s[i];
s[i] = s[j];
s[j] = tmp;
}
public static void main(String[] args) {
char[] s = {'a','b','c'};
permutation(s, 0, 2);
}
}