Add comparison between iteration and recursion.

Fix the figure of tail recursion.
Fix two links.

codes/python/chapter_computational_complexity/recursion.py

@@ -16,6 +16,23 @@ def recur(n: int) -> int:
     return n + res
 
 
+def for_loop_recur(n: int) -> int:
+    """使用迭代模拟递归"""
+    # 使用一个显式的栈来模拟系统调用栈
+    stack = []
+    res = 0
+    # 递：递归调用
+    for i in range(n, 0, -1):
+        # 通过“入栈操作”模拟“递”
+        stack.append(i)
+    # 归：返回结果
+    while stack:
+        # 通过“出栈操作”模拟“归”
+        res += stack.pop()
+    # res = 1+2+3+...+n
+    return res
+
+
 def tail_recur(n, res):
     """尾递归"""
     # 终止条件
@@ -42,6 +59,9 @@ if __name__ == "__main__":
     res = recur(n)
     print(f"\n递归函数的求和结果 res = {res}")
 
+    res = for_loop_recur(n)
+    print(f"\n使用迭代模拟递归求和结果 res = {res}")
+
     res = tail_recur(n, 0)
     print(f"\n尾递归函数的求和结果 res = {res}")