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
class Solution {
func longestCommonSubsequence(_ text1: String, _ text2: String) -> Int {
let text1 = Array(text1), text2 = Array(text2)
let n = text1.count
let m = text2.count
var dp = [Int](repeating: 0, count: m + 1)
for i in 0..<n {
var curRow = [Int](repeating: 0, count: m + 1)
for j in 0..<m {
if text1[i] == text2[j] {
curRow[j + 1] = 1 + dp[j]
} else {
curRow[j + 1] = max(dp[j + 1], curRow[j])
}
}
dp = curRow
}
return dp[m]
}
}