1143. Longest Common Subsequence #

Problem Statement: #

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.

Solution: #

public int longestCommonSubsequence(String str1, String str2) {
    int m = str1.length(),
        n = str2.length();
    int[][] dp = new int[m + 1][n + 1];
    for (int i = 0; i < m + 1; i++)
    for (int j = 0; j < n + 1; j++) {
        if (i == 0 || j == 0)
        dp[i][j] = 0;
        else if (str1.charAt(i - 1) == str2.charAt(j - 1))
        dp[i][j] = 1 + dp[i - 1][j - 1];
        else
        dp[i][j] = Math.max(dp[i - 1][j], dp[i][j - 1]);
    }
    return dp[m][n];
}

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