1143. Longest Common Subsequence

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 <= 1000
• text1 and text2 consist of only lowercase English characters.

1143. Longest Common Subsequence
struct Solution;

impl Solution {
fn longest_common_subsequence(text1: String, text2: String) -> i32 {
let s1: Vec<char> = text1.chars().collect();
let s2: Vec<char> = text2.chars().collect();
let n1 = s1.len();
let n2 = s2.len();
let mut dp: Vec<Vec<usize>> = vec![vec![0; n2 + 1]; n1 + 1];
for i in 0..n1 {
for j in 0..n2 {
if s1[i] == s2[j] {
dp[i + 1][j + 1] = dp[i][j] + 1;
} else {
dp[i + 1][j + 1] = dp[i][j + 1].max(dp[i + 1][j]);
}
}
}
dp[n1][n2] as i32
}
}

#[test]
fn test() {
let text1 = "abcde".to_string();
let text2 = "ace".to_string();
let res = 3;
assert_eq!(Solution::longest_common_subsequence(text1, text2), res);
let text1 = "abc".to_string();
let text2 = "abc".to_string();
let res = 3;
assert_eq!(Solution::longest_common_subsequence(text1, text2), res);
let text1 = "abc".to_string();
let text2 = "def".to_string();
let res = 0;
assert_eq!(Solution::longest_common_subsequence(text1, text2), res);
}