source code for chapter 4

shenzhun · shenzhun · commit 3371fa57b3af · 2013-08-08T17:06:36.000+08:00
diff --git a/ch04/__init__.py b/ch04/__init__.py
@@ -0,0 +1,3 @@
+__all__ = ['binary_search', 'binary_search_iterative', 'binary_sum', 'disk_usage',
+           'factorial', 'fibonacci', 'linear_sum', 'power_fast', 'power_slow',
+           'reverse', 'reverse_iterative', 'ruler', 'unique_bad']
diff --git a/ch04/binary_search.py b/ch04/binary_search.py
@@ -0,0 +1,38 @@
+# Copyright 2013, Michael H. Goldwasser
+#
+# Developed for use with the book:
+#
+#    Data Structures and Algorithms in Python
+#    Michael T. Goodrich, Roberto Tamassia, and Michael H. Goldwasser
+#    John Wiley & Sons, 2013
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+def binary_search(data, target, low, high):
+  """Return True if target is found in indicated portion of a Python list.
+
+  The search only considers the portion from data[low] to data[high] inclusive.
+  """
+  if low > high:
+    return False                    # interval is empty; no match
+  else:
+    mid = (low + high) // 2
+    if target == data[mid]:         # found a match
+      return True
+    elif target < data[mid]:
+      # recur on the portion left of the middle
+      return binary_search(data, target, low, mid - 1)
+    else:
+      # recur on the portion right of the middle
+      return binary_search(data, target, mid + 1, high)
diff --git a/ch04/binary_search_iterative.py b/ch04/binary_search_iterative.py
@@ -0,0 +1,34 @@
+# Copyright 2013, Michael H. Goldwasser
+#
+# Developed for use with the book:
+#
+#    Data Structures and Algorithms in Python
+#    Michael T. Goodrich, Roberto Tamassia, and Michael H. Goldwasser
+#    John Wiley & Sons, 2013
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+def binary_search_iterative(data, target):
+  """Return True if target is found in the given Python list."""
+  low = 0
+  high = len(data)-1
+  while low <= high:
+    mid = (low + high) // 2
+    if target == data[mid]:         # found a match
+      return True
+    elif target < data[mid]:
+      high = mid - 1                # only consider values left of mid
+    else:
+      low = mid + 1                 # only consider values right of mid
+  return False                      # loop ended without success
diff --git a/ch04/binary_sum.py b/ch04/binary_sum.py
@@ -0,0 +1,30 @@
+# Copyright 2013, Michael H. Goldwasser
+#
+# Developed for use with the book:
+#
+#    Data Structures and Algorithms in Python
+#    Michael T. Goodrich, Roberto Tamassia, and Michael H. Goldwasser
+#    John Wiley & Sons, 2013
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+def binary_sum(S, start, stop):
+  """Return the sum of the numbers in implicit slice S[start:stop]."""
+  if start >= stop:                      # zero elements in slice
+    return 0
+  elif start == stop-1:                  # one element in slice
+    return S[start]
+  else:                                  # two or more elements in slice
+    mid = (start + stop) // 2
+    return binary_sum(S, start, mid) + binary_sum(S, mid, stop)
diff --git a/ch04/disk_usage.py b/ch04/disk_usage.py
@@ -0,0 +1,33 @@
+# Copyright 2013, Michael H. Goldwasser
+#
+# Developed for use with the book:
+#
+#    Data Structures and Algorithms in Python
+#    Michael T. Goodrich, Roberto Tamassia, and Michael H. Goldwasser
+#    John Wiley & Sons, 2013
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import os
+
+def disk_usage(path):
+  """Return the number of bytes used by a file/folder and any descendents."""
+  total = os.path.getsize(path)                  # account for direct usage
+  if os.path.isdir(path):                        # if this is a directory,
+    for filename in os.listdir(path):            # then for each child:
+      childpath = os.path.join(path, filename)   # compose full path to child
+      total += disk_usage(childpath)             # add child's usage to total
+
+  print ('{0:<7}'.format(total), path)           # descriptive output (optional)
+  return total                                   # return the grand total
diff --git a/ch04/factorial.py b/ch04/factorial.py
@@ -0,0 +1,26 @@
+# Copyright 2013, Michael H. Goldwasser
+#
+# Developed for use with the book:
+#
+#    Data Structures and Algorithms in Python
+#    Michael T. Goodrich, Roberto Tamassia, and Michael H. Goldwasser
+#    John Wiley & Sons, 2013
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+def factorial(n):
+  if n == 0:
+    return 1
+  else:
+    return n * factorial(n-1)
diff --git a/ch04/fibonacci.py b/ch04/fibonacci.py
@@ -0,0 +1,35 @@
+# Copyright 2013, Michael H. Goldwasser
+#
+# Developed for use with the book:
+#
+#    Data Structures and Algorithms in Python
+#    Michael T. Goodrich, Roberto Tamassia, and Michael H. Goldwasser
+#    John Wiley & Sons, 2013
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+def bad_fibonacci(n):
+  """Return the nth Fibonacci number."""
+  if n <= 1:
+    return n
+  else:
+    return bad_fibonacci(n-2) + bad_fibonacci(n-1)
+
+def good_fibonacci(n):
+  """Return pair of Fibonacci numbers, F(n) and F(n-1)."""
+  if n <= 1:
+    return (n,0)
+  else:
+    (a, b) = good_fibonacci(n-1)
+    return (a+b, a)
diff --git a/ch04/linear_sum.py b/ch04/linear_sum.py
@@ -0,0 +1,27 @@
+# Copyright 2013, Michael H. Goldwasser
+#
+# Developed for use with the book:
+#
+#    Data Structures and Algorithms in Python
+#    Michael T. Goodrich, Roberto Tamassia, and Michael H. Goldwasser
+#    John Wiley & Sons, 2013
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+def linear_sum(S, n):
+  """Return the sum of the first n numbers of sequence S."""
+  if n == 0:
+    return 0
+  else:
+    return linear_sum(S, n-1) + S[n-1]
diff --git a/ch04/power_fast.py b/ch04/power_fast.py
@@ -0,0 +1,31 @@
+# Copyright 2013, Michael H. Goldwasser
+#
+# Developed for use with the book:
+#
+#    Data Structures and Algorithms in Python
+#    Michael T. Goodrich, Roberto Tamassia, and Michael H. Goldwasser
+#    John Wiley & Sons, 2013
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+def power(x, n):
+  """Compute the value x**n for integer n."""
+  if n == 0:
+    return 1
+  else:
+    partial = power(x, n // 2)          # rely on truncated division
+    result = partial * partial
+    if n % 2 == 1:                      # if n odd, include extra factor of x
+      result *= x                       
+    return result
diff --git a/ch04/power_slow.py b/ch04/power_slow.py
@@ -0,0 +1,27 @@
+# Copyright 2013, Michael H. Goldwasser
+#
+# Developed for use with the book:
+#
+#    Data Structures and Algorithms in Python
+#    Michael T. Goodrich, Roberto Tamassia, and Michael H. Goldwasser
+#    John Wiley & Sons, 2013
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+def power(x, n):
+  """Compute the value x**n for integer n."""
+  if n == 0:
+    return 1
+  else:
+    return x * power(x, n-1)
diff --git a/ch04/reverse.py b/ch04/reverse.py
@@ -0,0 +1,26 @@
+# Copyright 2013, Michael H. Goldwasser
+#
+# Developed for use with the book:
+#
+#    Data Structures and Algorithms in Python
+#    Michael T. Goodrich, Roberto Tamassia, and Michael H. Goldwasser
+#    John Wiley & Sons, 2013
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+def reverse(S, start, stop):
+  """Reverse elements in implicit slice S[start:stop]."""
+  if start < stop - 1:                         # if at least 2 elements:
+    S[start], S[stop-1] = S[stop-1], S[start]  # swap first and last
+    reverse(S, start+1, stop-1)                # recur on rest
diff --git a/ch04/reverse_iterative.py b/ch04/reverse_iterative.py
@@ -0,0 +1,27 @@
+# Copyright 2013, Michael H. Goldwasser
+#
+# Developed for use with the book:
+#
+#    Data Structures and Algorithms in Python
+#    Michael T. Goodrich, Roberto Tamassia, and Michael H. Goldwasser
+#    John Wiley & Sons, 2013
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+def reverse_iterative(S):
+  """Reverse elements in sequence S."""
+  start, stop = 0, len(S)
+  while start < stop - 1:
+    S[start], S[stop-1] = S[stop-1], S[start]  # swap first and last
+    start, stop = start + 1, stop - 1          # narrow the range
diff --git a/ch04/ruler.py b/ch04/ruler.py
@@ -0,0 +1,49 @@
+# Copyright 2013, Michael H. Goldwasser
+#
+# Developed for use with the book:
+#
+#    Data Structures and Algorithms in Python
+#    Michael T. Goodrich, Roberto Tamassia, and Michael H. Goldwasser
+#    John Wiley & Sons, 2013
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+def draw_line(tick_length, tick_label=''):
+  """Draw one line with given tick length (followed by optional label)."""
+  line = '-' * tick_length
+  if tick_label:
+    line += ' ' + tick_label
+  print(line)
+
+def draw_interval(center_length):
+  """Draw tick interval based upon a central tick length."""
+  if center_length > 0:                   # stop when length drops to 0
+    draw_interval(center_length - 1)      # recursively draw top ticks
+    draw_line(center_length)              # draw center tick
+    draw_interval(center_length - 1)      # recursively draw bottom ticks
+
+def draw_ruler(num_inches, major_length):
+  """Draw English ruler with given number of inches and major tick length."""
+  draw_line(major_length, '0')            # draw inch 0 line
+  for j in range(1, 1 + num_inches):
+    draw_interval(major_length - 1)       # draw interior ticks for inch
+    draw_line(major_length, str(j))       # draw inch j line and label
+
+
+if __name__ == '__main__':
+  draw_ruler(2,4)
+  print('='*30)
+  draw_ruler(1,5)
+  print('='*30)
+  draw_ruler(3,3)
diff --git a/ch04/unique_bad.py b/ch04/unique_bad.py

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+__all__ = ['binary_search', 'binary_search_iterative', 'binary_sum', 'disk_usage',`
	`2`	`+ 'factorial', 'fibonacci', 'linear_sum', 'power_fast', 'power_slow',`
	`3`	`+ 'reverse', 'reverse_iterative', 'ruler', 'unique_bad']`