D. Watch the video: <a href="http://www.rose-hulman.edu/class/csse/csse120/VideoFiles/11.3-PatternsForIteratingThroughSequences/Video/PatternsForIteratingThroughSequences/PatternsForIteratingThroughSequences.mp4" target=newtab><b>Sequences</b></a>, doing the next set of questions while you do so.
D. For the next set of questions, consider the following three function definitions:<pre>def foo1(seq):<br> total = 0<br> for k in range(len(seq) // 2):<br> total = total + seq[1 + (2 * k)]<br> return total<br><br><br>def foo2(seq):<br> total = 0<br> for k in range(1, len(seq), 2):<br> total = total + seq[k]<br> return total<br><br><br>def foo3(seq):<br> total = 0<br> m = 1<br> for _ in range(len(seq) // 2):<br> total = total + seq[m]<br> m = m + 2<br> return total<br></pre>
1. To what number does <code>foo1([3])</code> evaluate?
a. 0~
b. 1
c. 2
d. 3
e. 4
f. 5
g. 6
h. 7
i. 8
j. 9
k. 10
l. 11
m. 12
n. 13
o. 14
p. 15
q. 16
r. 17
r. 18
r. 19
r. 20
r. 24
r. 33
r. 38
1. To what number does <code>foo1([3, 6])</code> evaluate?
a. 0
b. 1
c. 2
d. 3
e. 4
f. 5
g. 6~
h. 7
i. 8
j. 9
k. 10
l. 11
m. 12
n. 13
o. 14
p. 15
q. 16
r. 17
r. 18
r. 19
r. 20
r. 24
r. 33
r. 38
1. To what number does <code>foo1([3, 6, 1, 4, 9, 5])</code> evaluate?
a. 0
b. 1
c. 2
d. 3
e. 4
f. 5
g. 6
h. 7
i. 8
j. 9
k. 10
l. 11
m. 12
n. 13
o. 14
p. 15~
q. 16
r. 17
r. 18
r. 19
r. 20
r. 24
r. 33
r. 38
1. To what number does <code>foo2([3])</code> evaluate?
a. 0~
b. 1
c. 2
d. 3
e. 4
f. 5
g. 6
h. 7
i. 8
j. 9
k. 10
l. 11
m. 12
n. 13
o. 14
p. 15
q. 16
r. 17
r. 18
r. 19
r. 20
r. 24
r. 33
r. 38
1. To what number does <code>foo2([3, 6])</code> evaluate?
a. 0
b. 1
c. 2
d. 3
e. 4
f. 5
g. 6~
h. 7
i. 8
j. 9
k. 10
l. 11
m. 12
n. 13
o. 14
p. 15
q. 16
r. 17
r. 18
r. 19
r. 20
r. 24
r. 33
r. 38
1. To what number does <code>foo2([3, 6, 1, 4, 9, 5])</code> evaluate?
a. 0
b. 1
c. 2
d. 3
e. 4
f. 5
g. 6
h. 7
i. 8
j. 9
k. 10
l. 11
m. 12
n. 13
o. 14
p. 15~
q. 16
r. 17
r. 18
r. 19
r. 20
r. 24
r. 33
r. 38
1. To what number does <code>foo3([3])</code> evaluate?
a. 0~
b. 1
c. 2
d. 3
e. 4
f. 5
g. 6
h. 7
i. 8
j. 9
k. 10
l. 11
m. 12
n. 13
o. 14
p. 15
q. 16
r. 17
r. 18
r. 19
r. 20
r. 24
r. 33
r. 38
1. To what number does <code>foo3([3, 6])</code> evaluate?
a. 0
b. 1
c. 2
d. 3
e. 4
f. 5
g. 6~
h. 7
i. 8
j. 9
k. 10
l. 11
m. 12
n. 13
o. 14
p. 15
q. 16
r. 17
r. 18
r. 19
r. 20
r. 24
r. 33
r. 38
1. To what number does <code>foo3([3, 6, 1, 4, 9, 5])</code> evaluate?
a. 0
b. 1
c. 2
d. 3
e. 4
f. 5
g. 6
h. 7
i. 8
j. 9
k. 10
l. 11
m. 12
n. 13
o. 14
p. 15~
q. 16
r. 17
r. 18
r. 19
r. 20
r. 24
r. 33
r. 38
D. For the next set of questions, consider the following two attempts at a function that returns the first negative item in the sequence of numbers, or <code>None</code> if the sequence contains no negative numbers. One is correct and the other is wrong. <pre>def find1(numbers):<br> for k in range(len(numbers)):<br> if numbers[k] < 0:<br> return numbers[k]<br> else:<br> return None<br><br><br>def find2(numbers):<br> for k in range(len(numbers)):<br> if numbers[k] < 0:<br> return numbers[k]<br> return None<br><br><br></pre>
1. To what number does <code>find1([-3, 6, 1, 4, 9, 5])</code> evaluate?
ANS. -3
1. To what number does <code>find2([-3, 6, 1, 4, 9, 5])</code> evaluate?
ANS. -3
1. To what number does <code>find1([3, 6, 1, 4, 9, 5])</code> evaluate?
ANS. None
1. To what number does <code>find2([3, 6, 1, 4, 9, 5])</code> evaluate?
ANS. None
1. To what number does <code>find1([3, -6, 1, 4, 9, 5])</code> evaluate?
ANS. None
1. To what number does <code>find2([3, -6, 1, 4, 9, 5])</code> evaluate?
ANS. -6
1. Which attempt is correct?
a. <code>find1</code>
b. <code>find2</code>~
D. For each of the following problems, indicate which pattern(s) is most suitable for a solution to the problem.
1. <pre>"""<br>What comes in:<br> -- a sequence of numbers<br>What goes out: Returns the INDEX of the first negative number<br> in the given sequence of numbers, or None if the sequence<br> contains no negative numbers.<br> Note: "first" negative number means the negative number<br> whose index is smallest -- see the examples.<br>Side effects: None.<br>Examples: If the argument is:<br> -- [4, 30, -19, 8, -3, -50, 100], this function returns 2<br> since the first negative number is -19, which is at index 2<br><br> -- [-8, 44, 33], this function returns 0<br> since the first negative number is -8, which is at index 0<br><br> -- [1, 29, 22, 8], this function returns None<br> since the list contains no negative numbers<br>"""</pre>
a. The FIND pattern~
b. The "Looking two places in the sequence at once" pattern
c. The "Looking at two sequences in parallel" pattern
d. The MAX/MIN pattern
1. <pre> """<br> What comes in:<br> -- a non-empty sequence of strings<br> What goes out: Returns the shortest string in the given sequence<br> of strings. If there is a tie for shortest string, returns the one<br> (among the ties) whose index is smallest.<br> Side effects: None.<br> Examples:<br> If the argument is:<br> ['all', 'we', 'are saying', 'is', 'give', 'peace', 'a chance']<br> then this function returns 'we'<br><br> If the argument is:<br> ['all we', 'are saying', 'is give', 'peace', 'a chance']<br> then this function returns 'peace'<br><br> If the argument is:<br> ['all we are saying', 'is give', 'peace a chance']<br> then this function returns 'is give'<br><br> If the argument is ['abc'], then this function returns 'abc'.<br> """</pre>
a. The FIND pattern
b. The "Looking two places in the sequence at once" pattern
c. The "Looking at two sequences in parallel" pattern
d. The MAX/MIN pattern~
1. <pre><br> """<br> What comes in:<br> -- a sequence of numbers<br> -- a positive integer n that is less than or equal to<br> the length of the given sequence<br> What goes out: INDEX of the largest number in the first n numbers<br> of the given sequence of numbers. If there is a tie for largest<br> number, returns the smallest of the indices of the tied numbers.<br> Side effects: None.<br> Examples:<br> If the first argument is:<br> [90, 0, 100, 200, -5, 100, -10, 200, 15]<br> and the second argument n is 3,<br> then this function returns 2 (because 100, at index 2,<br> is the largest of the first 3 numbers in the list).<br><br> Another example: for the same list as above, but with n = 2,<br> this function returns 0 (because 90, at index 0,<br> is the largest of the first 2 numbers in the list).<br><br> Yet another example: For the same list as above, but with n = 9,<br> this function returns 3 (because 200, at indices 3 and 7,<br> is the largest of the first 9 numbers in the list,<br> and we break the tie in favor of the smaller index).<br> """</pre>
a. The FIND pattern
b. The "Looking two places in the sequence at once" pattern
c. The "Looking at two sequences in parallel" pattern
d. The MAX/MIN pattern~
1. <pre> """<br> What comes in:<br> -- a string s<br> What goes out: Returns the number of times a letter is repeated<br> twice-in-a-row in the given string s.<br> Side effects: None.<br> Examples:<br> -- number_of_stutters('xhhbrrs') returns 2<br> -- number_of_stutters('xxxx') returns 3<br> -- number_of_stutters('xaxaxa') returns 0<br> -- number_of_stutters('xxx yyy xxxx') returns 7<br> -- number_of_stutters('xxxyyyxxxx') returns 7<br> -- number_of_stutters('') returns 0<br> """</pre>
a. The FIND pattern
b. The "Looking two places in the sequence at once" pattern~
c. The "Looking at two sequences in parallel" pattern
d. The MAX/MIN pattern
1. <pre> """<br> What comes in:<br> -- a string s that (in this simple version of the palindrome<br> problem) contains only lower-case letters<br> (no spaces, no punctuation, no upper-case characters)<br> What goes out: Returns True if the given string s is a palindrome,<br> i.e., reads the same backwards as forwards.<br> Returns False if the given string s is not a palindrome.<br> Side effects: None.<br> Examples:<br> abba reads backwards as abba so it IS a palindrome<br> but<br> abbz reads backwards as zbba so it is NOT a palindrome<br><br> Here are two more examples: (Note: I have put spaces into the<br> strings for readability; the real problem is the string WITHOUT<br> the spaces.)<br> a b c d e x x e d c b a reads backwards as<br> a b c d e x x e d c b a<br> so it IS a palindrome<br> but<br> a b c d e x y e d c b a reads backwards as<br> a b c d e y x e d c b a<br> so it is NOT a palindrome<br> """</pre>
a. The FIND pattern~
b. The "Looking two places in the sequence at once" pattern~
c. The "Looking at two sequences in parallel" pattern
d. The MAX/MIN pattern
1. <pre> """<br> What comes in:<br> -- two sequences that have the same length<br> What goes out: Returns the number of indices at which the two<br> given sequences have the same item at that index.<br> Side effects: None.<br> Examples:<br> If the sequences are:<br> (11, 33, 83, 18, 30, 55)<br> (99, 33, 83, 19, 30, 44)<br> then this function returns 3<br> since the two sequences have the same item at:<br> -- index 1 (both are 33)<br> -- index 2 (both are 83)<br> -- index 4 (both are 30)<br><br> Another example: if the sequences are:<br> 'how are you today?'<br> 'HOW? r ex u tiday?'<br> then this function returns 8 since the sequences are the same<br> at indices 5 (both are 'r'), 10 (both are 'u'), 11 (both are ' '),<br> 12 (both are 't'), 14 (both are 'd'), 15 (both are 'a'),<br> 16 (both are 'y') and 17 (both are '?') -- 8 indices.<br> """</pre>
a. The FIND pattern
b. The "Looking two places in the sequence at once" pattern
c. The "Looking at two sequences in parallel" pattern~
d. The MAX/MIN pattern