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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,95 @@ | ||
| from link import * | ||
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| def length(s): | ||
| """Return the number of elements in linked list s. | ||
| >>> length(Link(3, Link(4, Link(5)))) | ||
| 3 | ||
| """ | ||
| if s is Link.empty: | ||
| return 0 | ||
| else: | ||
| return 1 + length(s.rest) | ||
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| def length_iter(s): | ||
| """Return the number of elements in linked list s. | ||
| >>> length_iter(Link(3, Link(4, Link(5)))) | ||
| 3 | ||
| """ | ||
| k = 0 | ||
| while s is not Link.empty: | ||
| s, k = s.rest, k + 1 | ||
| return k | ||
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| def append(s, x): | ||
| """Append x to the end of non-empty s and return None. | ||
| >>> s = Link(3, Link(4, Link(5))) | ||
| >>> append(s, 6) | ||
| >>> print(s) | ||
| <3 4 5 6> | ||
| """ | ||
| if s.rest: | ||
| append(s.rest, x) | ||
| else: | ||
| s.rest = Link(x) | ||
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| def append_iter(s, x): | ||
| """Append x to the end of non-empty s and return None. | ||
| >>> s = Link(3, Link(4, Link(5))) | ||
| >>> append_iter(s, 6) | ||
| >>> print(s) | ||
| <3 4 5 6> | ||
| """ | ||
| while s.rest: | ||
| s = s.rest | ||
| s.rest = Link(x) | ||
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| def pop(s, i): | ||
| """Remove and return element i from linked list s for positive i. | ||
| >>> t = Link(3, Link(4, Link(5, Link(6)))) | ||
| >>> pop(t, 2) | ||
| 5 | ||
| >>> pop(t, 2) | ||
| 6 | ||
| >>> pop(t, 1) | ||
| 4 | ||
| >>> t | ||
| Link(3) | ||
| """ | ||
| assert i > 0 and i < length(s) | ||
| for x in range(i-1): | ||
| s = s.rest | ||
| result = s.rest.first | ||
| s.rest = s.rest.rest | ||
| return result | ||
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| def range_link(start, end): | ||
| """Return a Link containing consecutive integers from start to end. | ||
| >>> range_link(3, 6) | ||
| Link(3, Link(4, Link(5))) | ||
| """ | ||
| if start >= end: | ||
| return Link.empty | ||
| else: | ||
| return Link(start, range_link(start + 1, end)) | ||
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| def range_link_iter(start, end): | ||
| """Return a Link containing consecutive integers from start to end. | ||
| >>> range_link_iter(3, 6) | ||
| Link(3, Link(4, Link(5))) | ||
| """ | ||
| s = Link.empty | ||
| k = end - 1 | ||
| while k >= start: | ||
| s = Link(k, s) | ||
| k -= 1 | ||
| return s |
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