Generic Algorithms

1
Generic Algorithms

• Andy Wang
• Data Structures, Algorithms, and Generic
  Programming

2
Generic Copy

• template ltclass I, class Jgt
• void g_copy(I src_begin, I src_end, J dest_begin)
  
• while (src_begin ! src_end)
• dest_begin src_begin
• g_copy(L.Begin(), L.End(), V.Begin())
• g_copy(A, A n, L.Begin())

3
Generic Find

• Sequential search
• template ltclass I, typename Tgt
• I g_find(I begin, I end, const T t)
• for ( begin ! end begin)
• if (t begin)
• return begin
• return end
• List_iterator g_find(L.Begin(), L.End(), t)
• Vector_iterator g_find(V.Begin(), V.End(), t)
• Array_iterator g_find(A, A size, t)

4
Generic Max

• template ltclass Igt
• I g_max_element(I begin, I end)
• I max(begin)
• while (begin ! end)
• if (max lt begin)
• max begin
• return max
• List_iterator g_max_element(L.Begin, L.End())
• Deque_iterator g_max_element(D.Begin, D.End())
• Array_iterator g_max_element(A, A size)

5
Generic Algorithms and Predicate Objects

• template ltclass I, class Pgt
• I g_max_element(I begin, I end, const P p)
• I max(begin)
• while (begin ! end)
• if (p(max, begin))
• max begin
• return max
• TGreaterThan ltsometypegt gt
• Vector_iterator g_max_element(V.Begin(),
  V.End(), gt)
• Deque_iterator g_max_element(D.Begin(),
  D.End(), gt)
• A_iterator g_max_element(A, A size, gt)

6
Generic Algorithms and Predicate Objects (2)

• Function classes may be passed to generic
  algorithm as template parameter
• Commonly used to pass predicate such as LessThan
• Also used for other function classes

7
Generic Algorithms and Predicate Objects (3)

• template ltclass I, class Pgt
• F g_for_each(I begin, I end, F f)
• while (begin ! end)
• f(begin)
• return f
• TListltchargt L
• makeuppercase muc
• g_for_each(L.Begin(), L.End(), muc)

8
Generic for_each

• class smartmakeuppercase
• public
• int count
• smartmakeuppercase() count(0)
• void operator() (char x)
• char y x
• x toupper(x)
• if (y ! x) count
• smartmakeuppercase smuc0, smuc1
• smuc1 g_for_each(L.Begin(), L.End(), smuc0)
• cout ltlt smuc1.count smuc0.count // number
  letters converted

9
Testing Generic Algorithms

• typedef char element_type
• TListltelement_typegt L
• TVectorltelement_typegt V
• TListltelement_typegtIterator L_iterator
• TVectorltelement_typegtIterator V_iterator
• g_copy(L.Begin(), L.End(), V.Begin())

10
Generic Simple Sort

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 8 2 7 3
11
Generic Simple Sort (2)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 8 2 7 3
12
Generic Simple Sort (3)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 8 2 7 3
13
Generic Simple Sort (4)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 8 2 7 3
14
Generic Simple Sort (5)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 8 2 7 3
15
Generic Simple Sort (6)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 8 2 7 3
16
Generic Simple Sort (7)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 8 2 7 3
17
Generic Simple Sort (8)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 8 2 7 3
18
Generic Simple Sort (9)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 8 2 7 3
19
Generic Simple Sort (10)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 8 2 7 3
20
Generic Simple Sort (11)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 8 2 7 3
21
Generic Simple Sort (12)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 2 8 7 3
22
Generic Simple Sort (13)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 2 8 7 3
23
Generic Simple Sort (14)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 2 8 7 3
24
Generic Simple Sort (15)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 2 8 7 3
25
Generic Simple Sort (16)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 2 8 7 3
26
Generic Simple Sort (17)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 2 8 7 3
27
Generic Simple Sort (18)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 2 3 7 8
28
Generic Simple Sort (19)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 2 3 7 8
29
Generic Simple Sort (20)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 2 3 7 8
30
Generic Simple Sort (21)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i)
• k i
• for (j i j ! end j)
• if (j lt k)
• k j
• swap(i, k)

1 2 3 7 8
31
Generic Simple Sort (22)

• template ltclass Tgt
• void g_simple_sort(I begin, I end)
• I i, j, k
• for (i begin i ! end i) // for each
  element
• k i
• // find the smallest element between i and end
• for (j i j ! end j)
• if (j lt k)
• // store the index of the smallest
• // element to k
• k j
• // swap ith element with k
• swap(i, k)

32
Generic Simple Sort (23)

• TListltintgt L
• g_simple_sort(L.Begin(), L.End())
• Running time O(n2)

33
Announcements

• For this week, the Th 2-3 office hour is moved to
  Fri 11-12
• On Monday (10/20) and Wednesday (10/22), the
  class will meet in MCH 201
• Assignment 3 is due next Monday