怎么才能写好递归？ - 黑马程序员技术交流社区

public static List<Department> findTopLevelDepartmentList() {
Department dept_1_1 = new Department();
dept_1_1.setId(new Long(11));
dept_1_1.setName("宣传部");
Department dept_1_2 = new Department();
dept_1_2.setId(new Long(12));
dept_1_2.setName("业务部");
Department dept_1_2_1 = new Department();
dept_1_2_1.setId(new Long(121));
dept_1_2_1.setName("业务一部");
Department dept_1_2_2 = new Department();
dept_1_2_2.setId(new Long(122));
dept_1_2_2.setName("业务二部");
dept_1_2_1.setParent(dept_1_2);
dept_1_2_2.setParent(dept_1_2);
Set<Department> children_0 = new LinkedHashSet<Department>();
children_0.add(dept_1_2_1);
children_0.add(dept_1_2_2);
dept_1_2.setChildren(children_0);
// ================================
Department dept_1 = new Department();
dept_1.setId(new Long(1));
dept_1.setName("市场部");
dept_1_1.setParent(dept_1);
dept_1_2.setParent(dept_1);
Set<Department> children_1 = new LinkedHashSet<Department>();
children_1.add(dept_1_1);
children_1.add(dept_1_2);
dept_1.setChildren(children_1);
// ---
Department dept_2_1 = new Department();
dept_2_1.setId(new Long(21));
dept_2_1.setName("开发一部");
Department dept_2_2 = new Department();
dept_2_2.setId((new Long(22)));
dept_2_2.setName("开发二部");
Department dept_2 = new Department();
dept_2.setId(new Long(2));
dept_2.setName("开发部");
dept_2_1.setParent(dept_2);
dept_2_2.setParent(dept_2);
Set<Department> children_2 = new LinkedHashSet<Department>();
children_2.add(dept_2_1);
children_2.add(dept_2_2);
dept_2.setChildren(children_2);
// ---
List<Department> depts = new ArrayList<Department>();
depts.add(dept_1);
depts.add(dept_2);
return depts;
}

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private void showTreeList(Collection<Department> topList) {
for (Department top : topList) {
// 顶点
System.out.println(top.getName());
// 子树
showTreeList(top.getChildren());
}
}

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/**
* 需求：有5个人坐在一起，问第五个人多少岁，他说比第4个人大2岁，第4个人比第3个人大2岁
* 第3个人比第二个人大2岁，第2个人又比第1个人大2岁，第一个人说他/她10岁，求第5个人多大。
*
* 分析：使用递归调用：递归调用是指所处理的问题的规模在递增或递减，并且有一个结束递归的条件,递归函数有返回值。
*/
class DiGui
{
//static int age;//定义成员变量：全局的；静态变量：被静态方法调用
public static void main(String[] args)
{
System.out.println(getAge(5));
}
public static int getAge(int i)
{
int age;
if(i==1)//递归结束的条件
{
age = 10;
}
else
age = getAge(--i)+2;//反复调用自身，使问题规模变小，趋于结束
return age;
}
}

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/**
* 需求：用递归方法求n！
* 分析：递归结束条件是变量为1时，返回1
*/
class DiGui1
{
public static void main(String[] args)
{
int n = 10;
System.out.println(n+"!="+muti(n));
}
public static int muti(int n)
{
int result;
if(n==1)//递归结束条件
result = 1;
else
result = muti(n-1)*n;//
return result;
}
}

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