[CS61A]Homework 1

1. from operator import add, sub
   
2. def a_plus_abs_b(a, b):
   
3.     if b < 0:
   
4.         f = sub
   
5.     else:
   
6.         f = add
   
7.     return f(a,b)
   
8. 
   
9. print(a_plus_abs_b(2,-3))

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1. def two_of_three(a, b, c):
   
2.     """Return x*x + y*y, where x and y are the two largest members of the
   
3.     positive numbers a, b, and c.
   
4. 
   
5.     >>> two_of_three(1, 2, 3)
   
6.     13
   
7.     >>> two_of_three(5, 3, 1)
   
8.     34
   
9.     >>> two_of_three(10, 2, 8)
   
10.     164
    
11.     >>> two_of_three(5, 5, 5)
    
12.     50
    
13.     """
    
14.     "*** YOUR CODE HERE ***"
    
15.     return max(a * a + b * b, a * a + c * c, b * b + c * c)
    
16. 
    
17. print(two_of_three(1, 2, 5))

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1. from operator import add, sub
   
2. import time
   
3. def a_plus_abs_b(a, b):
   
4.     """Return a+abs(b), but without calling abs.
   
5. 
   
6.     >>> a_plus_abs_b(2, 3)
   
7.     5
   
8.     >>> a_plus_abs_b(2, -3)
   
9.     5
   
10.     """
    
11.     if b < 0:
    
12.         return a - b
    
13.     else:
    
14.         return a + b
    
15.    
    
16. 
    
17. def two_of_three(a, b, c):
    
18.     """Return x*x + y*y, where x and y are the two largest members of the
    
19.     positive numbers a, b, and c.
    
20. 
    
21.     >>> two_of_three(1, 2, 3)
    
22.     13
    
23.     >>> two_of_three(5, 3, 1)
    
24.     34
    
25.     >>> two_of_three(10, 2, 8)
    
26.     164
    
27.     >>> two_of_three(5, 5, 5)
    
28.     50
    
29.     """
    
30.     "*** YOUR CODE HERE ***"
    
31. 
    
32.     if b <= a & b <= c:
    
33.             return a*a + c*c
    
34.     if c <= b & c <= a:
    
35.             return a*a +b*b
    
36.     else:
    
37.             return b*b + c*c
    
38. 
    
39.    
    
40. 
    
41. def if_function(condition, true_result, false_result):
    
42.     """Return true_result if condition is a true value, and
    
43.     false_result otherwise.
    
44. 
    
45.     >>> if_function(True, 2, 3)
    
46.     2
    
47.     >>> if_function(False, 2, 3)
    
48.     3
    
49.     >>> if_function(3==2, 3+2, 3-2)
    
50.     1
    
51.     >>> if_function(3>2, 3+2, 3-2)
    
52.     5
    
53.     """
    
54.     if condition:
    
55.         return true_result
    
56.     else:
    
57.         return false_result
    
58. 
    
59. def with_if_statement():
    
60.     """
    
61.     >>> with_if_statement()
    
62.     1
    
63.     """
    
64.     if c():
    
65.         return t()
    
66.     else:
    
67.         return f()
    
68. 
    
69. def with_if_function():
    
70.     return if_function(c(), t(), f())
    
71. 
    
72. def c():
    
73.     "*** YOUR CODE HERE ***"   
    
74.     return True
    
75. 
    
76. def t():
    
77.     "*** YOUR CODE HERE ***"
    
78.     return 1
    
79. 
    
80. def f():
    
81.     "*** YOUR CODE HERE ***"
    
82.     return 'shit' / 0
    
83. 
    
84. 
    
85. def hailstone(n):
    
86.     """Print the hailstone sequence starting at n and return its
    
87.     length.
    
88.     >>> a = hailstone(10)
    
89.     10
    
90.     5
    
91.     16
    
92.     8
    
93.     4
    
94.     2
    
95.     1
    
96.     >>> a
    
97.     7
    
98.     """
    
99.     "*** YOUR CODE HERE ***"
    
100.     length = 1
     
101.     while n != 1:
     
102.         print (int(n))
     
103.         if n % 2 == 0:
     
104.             n = n / 2
     
105.         else:
     
106.             n = 3*n + 1
     
107.         length = length + 1
     
108.     print (int(n))
     
109.     return length
     
110. 
     
111. 
     
112. challenge_question_program = """
     
113. "*** YOUR CODE HERE ***
     
114. """
     
115. s = 'print("s=" + repr(s) + ";eval(s)")';eval(s) return s

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第三问其实上面都不对，人家要求statement和function返回的结果不一样，你们返回都是一样的，我想了半天不会，整了个报错的。。。。。反正不一样。。。。最后一个不会写。。。太菜

lianyujia 发表于 2016-5-3 03:25
第三问其实上面都不对，人家要求statement和function返回的结果不一样，你们返回都是一样的，我想了半天不 ...

哈哈，不用谦虚，我还就会前两道呢，慢慢来就好

最后一问 challenge question想了一会儿没想出来。。。

1. 
   
2. from operator import add, sub
   
3. 
   
4. def a_plus_abs_b(a, b):
   
5.     """Return a+abs(b), but without calling abs.
   
6. 
   
7.     >>> a_plus_abs_b(2, 3)
   
8.     5
   
9.     >>> a_plus_abs_b(2, -3)
   
10.     5
    
11.     """
    
12.     if b < 0:
    
13.         f = sub(a,b)
    
14.     else:
    
15.         f = add(a,b)
    
16.     return f
    
17. 
    
18. def two_of_three(a, b, c):
    
19.     """Return x*x + y*y, where x and y are the two largest members of the
    
20.     positive numbers a, b, and c.
    
21. 
    
22.     >>> two_of_three(1, 2, 3)
    
23.     13
    
24.     >>> two_of_three(5, 3, 1)
    
25.     34
    
26.     >>> two_of_three(10, 2, 8)
    
27.     164
    
28.     >>> two_of_three(5, 5, 5)
    
29.     50
    
30.     """
    
31.     if a<b:
    
32.         a,b=b,a
    
33.     if a<c:
    
34.         a,c=c,a
    
35.     if b<c:
    
36.         b,c=c,b
    
37.     return a*a+b*b
    
38. 
    
39. 
    
40. def if_function(condition, true_result, false_result):
    
41.     """Return true_result if condition is a true value, and
    
42.     false_result otherwise.
    
43. 
    
44.     >>> if_function(True, 2, 3)
    
45.     2
    
46.     >>> if_function(False, 2, 3)
    
47.     3
    
48.     >>> if_function(3==2, 3+2, 3-2)
    
49.     1
    
50.     >>> if_function(3>2, 3+2, 3-2)
    
51.     5
    
52.     """
    
53.     if condition:
    
54.         return true_result
    
55.     else:
    
56.         return false_result
    
57. 
    
58. def with_if_statement():
    
59.     """
    
60.     >>> with_if_statement()
    
61.     1
    
62.     """
    
63.     if c():
    
64.         return t()
    
65.     else:
    
66.         return f()
    
67. 
    
68. def with_if_function():
    
69.     return if_function(c(), t(), f())
    
70. 
    
71. def c():
    
72.     return 1
    
73. 
    
74. def t():
    
75.     return 1
    
76. 
    
77. def f():
    
78.     "Return an variable diliberitely so that with_if_function with will return an error but with_if_statement will not"
    
79.     return error
    
80. 
    
81. def hailstone(n):
    
82.     """Print the hailstone sequence starting at n and return its
    
83.     length.
    
84. 
    
85.     >>> a = hailstone(10)
    
86.     10
    
87.     5
    
88.     16
    
89.     8
    
90.     4
    
91.     2
    
92.     1
    
93.     >>> a
    
94.     7
    
95.     """
    
96.     length=0
    
97.     while n>1:
    
98.         print(n)
    
99.         if n % 2==0:
    
100.             n=n//2
     
101.         else:
     
102.             n=3*n+1
     
103.         length+=1
     
104.     print(n)
     
105.     length+=1
     
106.     return length
     
107. 
     
108. challenge_question_program = """
     
109. "*** YOUR CODE HERE ***"
     
110. """
     
111. 
     
112. 
     

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from operator import add, sub

def a_plus_abs_b(a, b):
    """Return a+abs(b), but without calling abs.

    >>> a_plus_abs_b(2, 3)
    5
    >>> a_plus_abs_b(2, -3)
    5
    """
    if b < 0:
        f = sub(a, b)
    else:
        f = add(a, b)
    return f(a, b)

def two_of_three(a, b, c):
    """Return x*x + y*y, where x and y are the two largest members of the
    positive numbers a, b, and c.

    >>> two_of_three(1, 2, 3)
    13
    >>> two_of_three(5, 3, 1)
    34
    >>> two_of_three(10, 2, 8)
    164
    >>> two_of_three(5, 5, 5)
    50
    """
    if a <= b & b <= c:
        return b*b + c*c
    else:
        if b >= c:
            return a*a + b*b
        else:
            return a*a + c*c


def if_function(condition, true_result, false_result):
    """Return true_result if condition is a true value, and
    false_result otherwise.

    >>> if_function(True, 2, 3)
    2
    >>> if_function(False, 2, 3)
    3
    >>> if_function(3==2, 3+2, 3-2)
    1
    >>> if_function(3>2, 3+2, 3-2)
    5
    """
    if condition:
        return true_result
    else:
        return false_result

def with_if_statement():
    """
    >>> with_if_statement()
    1
    """
    if c():
        return t()
    else:
        return f()

def with_if_function():
    return if_function(c(), t(), f())

def c():
    return true

def t():
    return 1

def f():
    return

def hailstone(n):
    """Print the hailstone sequence starting at n and return its
    length.

    >>> a = hailstone(10)
    10
    5
    16
    8
    4
    2
    1
    >>> a
    7
    """
    print(n)
    i = 1
    while(n != 1):
        if n%2 == 0:
            n = n/2
            print(n)
        else:
            n = n * 3 + 1
            print(n)
        i = i + 1
    return i


challenge_question_program = """
s = 'print("s = " + repr(s) + "; eval(s)")'; eval(s)
"""

rarezhang 发表于 2015-5-7 12:28
交作业： https://bitbucket.org/rarezhang/ucberkely_cs61a/src/63ddd9c4e7f39a8f5abcde757f3c86530dcede2 ...

哈哈，hailstone和我一样直接想到递归，我当时都忘了这门课还没讲递归呢

1. from operator import add, sub
   
2. 
   
3. def a_plus_abs_b(a, b):
   
4.     """Return a+abs(b), but without calling abs.
   
5. 
   
6.     >>> a_plus_abs_b(2, 3)
   
7.     5
   
8.     >>> a_plus_abs_b(2, -3)
   
9.     5
   
10.     """
    
11.     if b < 0:
    
12.         f = sub
    
13.     else:
    
14.         f = add
    
15.     return f(a, b)
    
16. 
    
17. def two_of_three(a, b, c):
    
18.     """Return x*x + y*y, where x and y are the two largest members of the
    
19.     positive numbers a, b, and c.
    
20. 
    
21.     >>> two_of_three(1, 2, 3)
    
22.     13
    
23.     >>> two_of_three(5, 3, 1)
    
24.     34
    
25.     >>> two_of_three(10, 2, 8)
    
26.     164
    
27.     >>> two_of_three(5, 5, 5)
    
28.     50
    
29.     """
    
30.     assert a > 0 and b > 0 and c > 0
    
31.     list = [a, b, c]
    
32.     list.remove(max(list))
    
33.     return pow(max(a, b,c),2) + pow(max(list),2)
    
34. 
    
35. def if_function(condition, true_result, false_result):
    
36.     """Return true_result if condition is a true value, and
    
37.     false_result otherwise.
    
38. 
    
39.     >>> if_function(True, 2, 3)
    
40.     2
    
41.     >>> if_function(False, 2, 3)
    
42.     3
    
43.     >>> if_function(3==2, 3+2, 3-2)
    
44.     1
    
45.     >>> if_function(3>2, 3+2, 3-2)
    
46.     5
    
47.     """
    
48.     if condition:
    
49.         return true_result
    
50.     else:
    
51.         return false_result
    
52. 
    
53. def with_if_statement():
    
54.     """
    
55.     >>> with_if_statement()
    
56.     1
    
57.     """
    
58.     if c():
    
59.         return t()
    
60.     else:
    
61.         return f()
    
62. 
    
63. def with_if_function():
    
64.     return if_function(c(), t(), f())
    
65. 
    
66. def c():
    
67.     "*** YOUR CODE HERE ***"
    
68.     return False
    
69. 
    
70. def t():
    
71.     "*** YOUR CODE HERE ***"
    
72.     return 0
    
73. 
    
74. def f():
    
75.     "*** YOUR CODE HERE ***"
    
76.     return 1
    
77. 
    
78. def hailstone(n):
    
79.     """Print the hailstone sequence starting at n and return its
    
80.     length.
    
81. 
    
82.     >>> a = hailstone(10)
    
83.     10
    
84.     5
    
85.     16
    
86.     8
    
87.     4
    
88.     2
    
89.     1
    
90.     >>> a
    
91.     7
    
92.     """
    
93.     "*** YOUR CODE HERE ***"
    
94.     assert n > 0
    
95.     k = 1
    
96.     print(n)
    
97.     while n != 1:
    
98.         k = k + 1
    
99.         if n % 2 == 0:
    
100.             n = int(n / 2)
     
101.         else:
     
102.             n = 3 * n + 1
     
103.         print(n)
     
104.     return k
     
105.         
     
106.    
     
107. 
     
108. challenge_question_program = """
     
109. "*** YOUR CODE HERE ***"
     
110. """
     
111. s = 'print("s = " + repr(s) + "; eval(s)")'; eval(s)
     
112. 
     
113. 
     

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1. from operator import add, sub
   
2. 
   
3. def a_plus_abs_b(a, b):
   
4.     """Return a+abs(b), but without calling abs.
   
5. 
   
6.     >>> a_plus_abs_b(2, 3)
   
7.     5
   
8.     >>> a_plus_abs_b(2, -3)
   
9.     5
   
10.     """
    
11.     if b < 0:
    
12.         f = sub
    
13.     else:
    
14.         f = add
    
15.     return f(a, b)
    
16. 
    
17. def two_of_three(a, b, c):
    
18.     """Return x*x + y*y, where x and y are the two largest members of the
    
19.     positive numbers a, b, and c.
    
20. 
    
21.     >>> two_of_three(1, 2, 3)
    
22.     13
    
23.     >>> two_of_three(5, 3, 1)
    
24.     34
    
25.     >>> two_of_three(10, 2, 8)
    
26.     164
    
27.     >>> two_of_three(5, 5, 5)
    
28.     50
    
29.     """
    
30.     return sub(a*a+b*b+c*c, min(a, b, c)*min(a, b, c))
    
31. 
    
32. def largest_factor(n):
    
33.     """Return the largest factor of n that is smaller than n.
    
34. 
    
35.     >>> largest_factor(15) # factors are 1, 3, 5
    
36.     5
    
37.     >>> largest_factor(80) # factors are 1, 2, 4, 5, 8, 10, 16, 20, 40
    
38.     40
    
39.     >>> largest_factor(13) # factor is 1 since 13 is prime
    
40.     1
    
41.     """
    
42.     largest_factor = 1
    
43.     for i in range(1,n):
    
44.         if n%i == 0:
    
45.             largest_factor = i
    
46.     return largest_factor
    
47. 
    
48. def if_function(condition, true_result, false_result):
    
49.     """Return true_result if condition is a true value, and
    
50.     false_result otherwise.
    
51. 
    
52.     >>> if_function(True, 2, 3)
    
53.     2
    
54.     >>> if_function(False, 2, 3)
    
55.     3
    
56.     >>> if_function(3==2, 3+2, 3-2)
    
57.     1
    
58.     >>> if_function(3>2, 3+2, 3-2)
    
59.     5
    
60.     """
    
61.     if condition:
    
62.         return true_result
    
63.     else:
    
64.         return false_result
    
65. 
    
66. 
    
67. def with_if_statement():
    
68.     """
    
69.     >>> with_if_statement()
    
70.     1
    
71.     """
    
72.     if c():
    
73.         return t()
    
74.     else:
    
75.         return f()
    
76. 
    
77. def with_if_function():
    
78.     return if_function(c(), t(), f())
    
79. 
    
80. def c():
    
81.     "*** YOUR CODE HERE ***"
    
82.     return True
    
83. 
    
84. def t():
    
85.     "*** YOUR CODE HERE ***"
    
86.     return 1
    
87. 
    
88. def f():
    
89.     "*** YOUR CODE HERE ***"
    
90.     return RuntimeError
    
91. 
    
92. def hailstone(n):
    
93.     """Print the hailstone sequence starting at n and return its
    
94.     length.
    
95. 
    
96.     >>> a = hailstone(10)
    
97.     10
    
98.     5
    
99.     16
    
100.     8
     
101.     4
     
102.     2
     
103.     1
     
104.     >>> a
     
105.     7
     
106.     """
     
107.     "*** YOUR CODE HERE ***"
     
108.     count = 0
     
109.     while True:
     
110.         print(n)
     
111.         count = count+1
     
112.         if n == 1:
     
113.             break
     
114.         if n%2 == 0:
     
115.             n = n/2
     
116.         else:
     
117.             n = 3*n+1
     
118.     return count
     
119.    
     

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最后一题，是之前s已经存储好了，直接执行eval(s),然后执行的时候s='print("s="......;eval(s)")',所以repr的时候已经是整个语句了吧？？