LeetCode-in-All
1143. Longest Common Subsequence
Medium
Given two strings text1 and text2, return the length of their longest common subsequence. If there is no common subsequence, return 0.
A subsequence of a string is a new string generated from the original string with some characters (can be none) deleted without changing the relative order of the remaining characters.
- For example,
"ace"is a subsequence of"abcde".
A common subsequence of two strings is a subsequence that is common to both strings.
Example 1:
Input: text1 = “abcde”, text2 = “ace”
Output: 3
Explanation: The longest common subsequence is “ace” and its length is 3.
Example 2:
Input: text1 = “abc”, text2 = “abc”
Output: 3
Explanation: The longest common subsequence is “abc” and its length is 3.
Example 3:
Input: text1 = “abc”, text2 = “def”
Output: 0
Explanation: There is no such common subsequence, so the result is 0.
Constraints:
1 <= text1.length, text2.length <= 1000text1andtext2consist of only lowercase English characters.
Solution
# @param {String} text1
# @param {String} text2
# @return {Integer}
def longest_common_subsequence(text1, text2)
n = text1.length
m = text2.length
dp = Array.new(n + 1) {Array.new(m + 1, 0)}
(1..n).each do |i|
(1..m).each do |j|
if text1[i - 1] == text2[j - 1]
dp[i][j] = dp[i - 1][j - 1] + 1
else
dp[i][j] = [dp[i - 1][j], dp[i][j - 1]].max
end
end
end
dp[n][m]
end