输入一个字符串,按字典序打印出该字符串中字符的所有排列。
例如输入字符串abc,则打印出由字符a,b,c所能排列出来的所有字符串abc,acb,bac,bca,cab和cba。
import java.util.*;
public class Solution {
public ArrayList<String> Permutation(String str) {
ArrayList<String> result = new ArrayList<String>() ;
if(str == null || str.length() == 0) { return result ; }
char[] chars = str.toCharArray();
TreeSet<String> temp = new TreeSet<>();
Permutation(chars, 0, temp);
result.addAll(temp);
return result;
}
public void Permutation(char[] chars, int begin, TreeSet<String> result) {
if(chars==null || chars.length==0 || begin<0 || begin>chars.length-1) {
return;
}
if(begin == chars.length-1) {
result.add(String.valueOf(chars)) ;
}else {
for(int i=begin ; i<=chars.length-1 ; i++) {
swap(chars, begin, i) ;
Permutation(chars, begin+1, result);
swap(chars, begin, i) ;
}
}
}
public void swap(char[] x, int a, int b) {
char t = x[a];
x[a] = x[b];
x[b] = t;
}
}
