Polish the content

Polish the chapter preface, introduction and complexity anlysis

codes/python/chapter_computational_complexity/space_complexity.py

@@ -35,9 +35,9 @@ def linear(n: int):
     # 长度为 n 的列表占用 O(n) 空间
     nums = [0] * n
     # 长度为 n 的哈希表占用 O(n) 空间
-    mapp = dict[int, str]()
+    hmap = dict[int, str]()
     for i in range(n):
-        mapp[i] = str(i)
+        hmap[i] = str(i)
 
 
 def linear_recur(n: int):

codes/python/chapter_computational_complexity/time_complexity.py

@@ -61,7 +61,7 @@ def exponential(n: int) -> int:
     """指数阶（循环实现）"""
     count = 0
     base = 1
-    # cell 每轮一分为二，形成数列 1, 2, 4, 8, ..., 2^(n-1)
+    # 细胞每轮一分为二，形成数列 1, 2, 4, 8, ..., 2^(n-1)
     for _ in range(n):
         for _ in range(base):
             count += 1