mirror of
https://github.com/krahets/hello-algo.git
synced 2024-12-25 12:36:30 +08:00
78 lines
2 KiB
C#
78 lines
2 KiB
C#
/**
|
|
* File: recursion.cs
|
|
* Created Time: 2023-08-28
|
|
* Author: hpstory (hpstory1024@163.com)
|
|
*/
|
|
|
|
namespace hello_algo.chapter_computational_complexity;
|
|
|
|
public class recursion {
|
|
/* 递归 */
|
|
public int recur(int n) {
|
|
// 终止条件
|
|
if (n == 1)
|
|
return 1;
|
|
// 递:递归调用
|
|
int res = recur(n - 1);
|
|
// 归:返回结果
|
|
return n + res;
|
|
}
|
|
|
|
/* 使用迭代模拟递归 */
|
|
public int forLoopRecur(int n) {
|
|
// 使用一个显式的栈来模拟系统调用栈
|
|
Stack<int> stack = new Stack<int>();
|
|
int res = 0;
|
|
// 递:递归调用
|
|
for (int i = n; i > 0; i--) {
|
|
// 通过“入栈操作”模拟“递”
|
|
stack.Push(i);
|
|
}
|
|
// 归:返回结果
|
|
while (stack.Count > 0) {
|
|
// 通过“出栈操作”模拟“归”
|
|
res += stack.Pop();
|
|
}
|
|
// res = 1+2+3+...+n
|
|
return res;
|
|
}
|
|
|
|
/* 尾递归 */
|
|
public int tailRecur(int n, int res) {
|
|
// 终止条件
|
|
if (n == 0)
|
|
return res;
|
|
// 尾递归调用
|
|
return tailRecur(n - 1, res + n);
|
|
}
|
|
|
|
/* 斐波那契数列:递归 */
|
|
public int fib(int n) {
|
|
// 终止条件 f(1) = 0, f(2) = 1
|
|
if (n == 1 || n == 2)
|
|
return n - 1;
|
|
// 递归调用 f(n) = f(n-1) + f(n-2)
|
|
int res = fib(n - 1) + fib(n - 2);
|
|
// 返回结果 f(n)
|
|
return res;
|
|
}
|
|
|
|
/* Driver Code */
|
|
[Test]
|
|
public void Test() {
|
|
int n = 5;
|
|
int res;
|
|
|
|
res = recur(n);
|
|
Console.WriteLine("\n递归函数的求和结果 res = " + res);
|
|
|
|
res = forLoopRecur(n);
|
|
Console.WriteLine("\n使用迭代模拟递归求和结果 res = " + res);
|
|
|
|
res = tailRecur(n, 0);
|
|
Console.WriteLine("\n尾递归函数的求和结果 res = " + res);
|
|
|
|
res = fib(n);
|
|
Console.WriteLine("\n斐波那契数列的第 " + n + " 项为 " + res);
|
|
}
|
|
}
|