Edit Distance

Given two strings word1 and word2, return the minimum number of operations required to convert word1 to word2.

You have the following three operations permitted on a word:

  • Insert a character
  • Delete a character
  • Replace a character

 

Example 1:

Input: word1 = "horse", word2 = "ros"
Output: 3
Explanation: 
horse -> rorse (replace 'h' with 'r')
rorse -> rose (remove 'r')
rose -> ros (remove 'e')

Example 2:

Input: word1 = "intention", word2 = "execution"
Output: 5
Explanation: 
intention -> inention (remove 't')
inention -> enention (replace 'i' with 'e')
enention -> exention (replace 'n' with 'x')
exention -> exection (replace 'n' with 'c')
exection -> execution (insert 'u')

 

Constraints:

  • 0 <= word1.length, word2.length <= 500
  • word1 and word2 consist of lowercase English letters.
SOLUTION:
class Solution:
    def md(self, word1, word2, i1, i2):
        if (i1, i2) in self.cache:
            return self.cache[(i1, i2)]
        if i1 == len(word1):
            return len(word2) - i2
        if i2 == len(word2):
            return len(word1) - i1
        if word1[i1] == word2[i2]:
            self.cache[(i1, i2)] = self.md(word1, word2, i1 + 1, i2 + 1)
            return self.cache[(i1, i2)]
        else:
            self.cache[(i1, i2)] = 1 + min(self.md(word1, word2, i1 + 1, i2 + 1), self.md(word1, word2, i1, i2 + 1), self.md(word1, word2, i1 + 1, i2))
            return self.cache[(i1, i2)]
    
    def minDistance(self, word1: str, word2: str) -> int:
        self.cache = {}
        return self.md(word1, word2, 0, 0)

Comments

Post a Comment

Popular posts from this blog

Encrypt and Decrypt Strings

You are given a character array keys containing unique characters and a string array values containing strings of length 2. You are also given another string array dictionary that contains all permitted original strings after decryption. You should implement a data structure that can encrypt or decrypt a 0-indexed string. A string is encrypted with the following process: For each character c in the string, we find the index i satisfying keys[i] == c in keys . Replace c with values[i] in the string. Note that in case a character of the string is not present in keys , the encryption process cannot be carried out, and an empty string "" is returned. A string is decrypted with the following process: For each substring s of length 2 occurring at an even index in the string, we find an i such that values[i] == s . If there are multiple valid i , we choose any one of them. This means a string could have multiple possible strings it can decrypt t...
Read more

Degree of an Array

Given a non-empty array of non-negative integers nums , the degree of this array is defined as the maximum frequency of any one of its elements. Your task is to find the smallest possible length of a (contiguous) subarray of nums , that has the same degree as nums .   Example 1: Input: nums = [1,2,2,3,1] Output: 2 Explanation: The input array has a degree of 2 because both elements 1 and 2 appear twice. Of the subarrays that have the same degree: [1, 2, 2, 3, 1], [1, 2, 2, 3], [2, 2, 3, 1], [1, 2, 2], [2, 2, 3], [2, 2] The shortest length is 2. So return 2. Example 2: Input: nums = [1,2,2,3,1,4,2] Output: 6 Explanation: The degree is 3 because the element 2 is repeated 3 times. So [2,2,3,1,4,2] is the shortest subarray, therefore returning 6.   Constraints: nums.length will be between 1 and 50,000. nums[i] will be an integer between 0 and 49,999. SOLUTION: from collections import defaultdict class Solution : def findShortestSubArr...
Read more

Minimum Sum of Four Digit Number After Splitting Digits

You are given a positive integer num consisting of exactly four digits. Split num into two new integers new1 and new2 by using the digits found in num . Leading zeros are allowed in new1 and new2 , and all the digits found in num must be used. For example, given num = 2932 , you have the following digits: two 2 's, one 9 and one 3 . Some of the possible pairs [new1, new2] are [22, 93] , [23, 92] , [223, 9] and [2, 329] . Return the minimum possible sum of new1 and new2 .   Example 1: Input: num = 2932 Output: 52 Explanation: Some possible pairs [new1, new2] are [29, 23], [223, 9], etc. The minimum sum can be obtained by the pair [29, 23]: 29 + 23 = 52. Example 2: Input: num = 4009 Output: 13 Explanation: Some possible pairs [new1, new2] are [0, 49], [490, 0], etc. The minimum sum can be obtained by the pair [4, 9]: 4 + 9 = 13.   Constraints: 1000 <= num <= 9999 SOLUTION: class Solution : def minimumSum ( self,...
Read more