README.md

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.

Solutions (Rust)

1. Solution

impl Solution {
    pub fn longest_common_subsequence(text1: String, text2: String) -> i32 {
        let text1 = text1.as_bytes();
        let text2 = text2.as_bytes();
        let mut dp = vec![vec![0; text2.len()]; text1.len()];

        for i in 0..text1.len() {
            for j in 0..text2.len() {
                if text1[i] == text2[j] {
                    if i > 0 && j > 0 {
                        dp[i][j] = dp[i - 1][j - 1];
                    }
                    dp[i][j] += 1;
                }
                if i > 0 {
                    dp[i][j] = dp[i][j].max(dp[i - 1][j]);
                }
                if j > 0 {
                    dp[i][j] = dp[i][j].max(dp[i][j - 1]);
                }
            }
        }

        dp[text1.len() - 1][text2.len() - 1]
    }
}