递归实现的全排列算法

import java.util.ArrayList;
import java.util.List;

public class Test {
public static void main(String[] args) {
String[] arr = { "1", "2", "3" };
List<Object[]> result = new ArrayList<Object[]>();
permArr(arr, 0, result);
for (int i = 0; i < result.size(); i++) {
Object[] temp = (Object[]) result.get(i);
for (int j = 0; j < temp.length; j++) {
System.out.print(temp[j]);
}
System.out.println();
}
}

public static void permArr(Object[] arr, int level, List<Object[]> container) {
if (level == arr.length - 1) {
Object[] tempArr = new Object[arr.length];
System.arraycopy(arr, 0, tempArr, 0, arr.length);
container.add(tempArr);
} else {
for (int i = level; i < arr.length; i++) {
swap(arr, i, level);
permArr(arr, level + 1, container);
swap(arr, i, level);
}
}
}

private static void swap(Object arr[], int i, int j) { // 通过临时变量,交换数据
if (i < 0 || j < 0 || i >= arr.length || j >= arr.length || i == j)
return;
Object tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
arr[j] = tmp;
}

}

结果：

123
132
213
231
321
312