@@ -19,74 +19,72 @@ class EditDistance:
1919 """
2020
2121 def __init__ (self ):
22- self .__prepare__ ()
23-
24- def __prepare__ (self , n = 0 , m = 0 ):
25- self .dp = [[- 1 for y in range (0 , m )] for x in range (0 , n )]
26-
27- def __solve_dp (self , x , y ):
28- if x == - 1 :
29- return y + 1
30- elif y == - 1 :
31- return x + 1
32- elif self .dp [x ][y ] > - 1 :
33- return self .dp [x ][y ]
22+ self .word1 = ""
23+ self .word2 = ""
24+ self .dp = []
25+
26+ def __min_dist_top_down_dp (self , m : int , n : int ) -> int :
27+ if m == - 1 :
28+ return n + 1
29+ elif n == - 1 :
30+ return m + 1
31+ elif self .dp [m ][n ] > - 1 :
32+ return self .dp [m ][n ]
3433 else :
35- if self .a [ x ] == self .b [ y ]:
36- self .dp [x ][ y ] = self .__solve_dp ( x - 1 , y - 1 )
34+ if self .word1 [ m ] == self .word2 [ n ]:
35+ self .dp [m ][ n ] = self .__min_dist_top_down_dp ( m - 1 , n - 1 )
3736 else :
38- self .dp [x ][y ] = 1 + min (
39- self .__solve_dp (x , y - 1 ),
40- self .__solve_dp (x - 1 , y ),
41- self .__solve_dp (x - 1 , y - 1 ),
42- )
43-
44- return self .dp [x ][y ]
45-
46- def solve (self , a , b ):
47- if isinstance (a , bytes ):
48- a = a .decode ("ascii" )
49-
50- if isinstance (b , bytes ):
51- b = b .decode ("ascii" )
52-
53- self .a = str (a )
54- self .b = str (b )
55-
56- self .__prepare__ (len (a ), len (b ))
57-
58- return self .__solve_dp (len (a ) - 1 , len (b ) - 1 )
59-
60-
61- def min_distance_bottom_up (word1 : str , word2 : str ) -> int :
62- """
63- >>> min_distance_bottom_up("intention", "execution")
64- 5
65- >>> min_distance_bottom_up("intention", "")
66- 9
67- >>> min_distance_bottom_up("", "")
68- 0
69- """
70- m = len (word1 )
71- n = len (word2 )
72- dp = [[0 for _ in range (n + 1 )] for _ in range (m + 1 )]
73- for i in range (m + 1 ):
74- for j in range (n + 1 ):
75-
76- if i == 0 : # first string is empty
77- dp [i ][j ] = j
78- elif j == 0 : # second string is empty
79- dp [i ][j ] = i
80- elif (
81- word1 [i - 1 ] == word2 [j - 1 ]
82- ): # last character of both substing is equal
83- dp [i ][j ] = dp [i - 1 ][j - 1 ]
84- else :
85- insert = dp [i ][j - 1 ]
86- delete = dp [i - 1 ][j ]
87- replace = dp [i - 1 ][j - 1 ]
88- dp [i ][j ] = 1 + min (insert , delete , replace )
89- return dp [m ][n ]
37+ insert = self .__min_dist_top_down_dp (m , n - 1 )
38+ delete = self .__min_dist_top_down_dp (m - 1 , n )
39+ replace = self .__min_dist_top_down_dp (m - 1 , n - 1 )
40+ self .dp [m ][n ] = 1 + min (insert , delete , replace )
41+
42+ return self .dp [m ][n ]
43+
44+ def min_dist_top_down (self , word1 : str , word2 : str ) -> int :
45+ """
46+ >>> EditDistance().min_dist_top_down("intention", "execution")
47+ 5
48+ >>> EditDistance().min_dist_top_down("intention", "")
49+ 9
50+ >>> EditDistance().min_dist_top_down("", "")
51+ 0
52+ """
53+ self .word1 = word1
54+ self .word2 = word2
55+ self .dp = [[- 1 for _ in range (len (word2 ))] for _ in range (len (word1 ))]
56+
57+ return self .__min_dist_top_down_dp (len (word1 ) - 1 , len (word2 ) - 1 )
58+
59+ def min_dist_bottom_up (self , word1 : str , word2 : str ) -> int :
60+ """
61+ >>> EditDistance().min_dist_bottom_up("intention", "execution")
62+ 5
63+ >>> EditDistance().min_dist_bottom_up("intention", "")
64+ 9
65+ >>> EditDistance().min_dist_bottom_up("", "")
66+ 0
67+ """
68+ self .word1 = word1
69+ self .word2 = word2
70+ m = len (word1 )
71+ n = len (word2 )
72+ self .dp = [[0 for _ in range (n + 1 )] for _ in range (m + 1 )]
73+
74+ for i in range (m + 1 ):
75+ for j in range (n + 1 ):
76+ if i == 0 : # first string is empty
77+ self .dp [i ][j ] = j
78+ elif j == 0 : # second string is empty
79+ self .dp [i ][j ] = i
80+ elif word1 [i - 1 ] == word2 [j - 1 ]: # last characters are equal
81+ self .dp [i ][j ] = self .dp [i - 1 ][j - 1 ]
82+ else :
83+ insert = self .dp [i ][j - 1 ]
84+ delete = self .dp [i - 1 ][j ]
85+ replace = self .dp [i - 1 ][j - 1 ]
86+ self .dp [i ][j ] = 1 + min (insert , delete , replace )
87+ return self .dp [m ][n ]
9088
9189
9290if __name__ == "__main__" :
@@ -99,7 +97,7 @@ def min_distance_bottom_up(word1: str, word2: str) -> int:
9997 S2 = input ("Enter the second string: " ).strip ()
10098
10199 print ()
102- print (f"The minimum Edit Distance is: { solver .solve (S1 , S2 )} )
103- print (f"The minimum Edit Distance is: { min_distance_bottom_up (S1 , S2 )} )
100+ print (f"The minimum edit distance is: { solver .min_dist_top_down (S1 , S2 )} )
101+ print (f"The minimum edit distance is: { solver . min_dist_bottom_up (S1 , S2 )} )
104102 print ()
105103 print ("*************** End of Testing Edit Distance DP Algorithm ***************" )
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