LeetCode-in-All
72. Edit Distance
Hard
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 <= 500word1andword2consist of lowercase English letters.
Solution
# @param {String} word1
# @param {String} word2
# @return {Integer}
def min_distance(word1, word2)
n1 = word1.length
n2 = word2.length
return min_distance(word2, word1) if n2 > n1
dp = Array.new(n2 + 1) {|j| j}
(1..n1).each do |i|
pre = dp[0]
dp[0] = i
(1..n2).each do |j|
tmp = dp[j]
dp[j] = word1[i - 1] != word2[j - 1] ? 1 + [pre, dp[j], dp[j - 1]].min : pre
pre = tmp
end
end
dp[n2]
end