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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: 3Explanation: The longest common subsequence is "abc" and its length is 3.

Example 3:

Input: text1 = "abc", text2 = "def"Output: 0Explanation: 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.

My solution​

/**
 * @param {string} text1
 * @param {string} text2
 * @return {number}
 */
var longestCommonSubsequence = function(text1, text2) {
    const dp = [];
    
    for (let i = 0; i <= text1.length; i++) {
        dp.push(new Array(text2.length + 1).fill(0))
    }
    
    for (let i = 1; i <= text1.length; i++)  {
        for (let j = 1; j <= text2.length; j++) {
            if (text1.charAt(i -1) === text2.charAt(j - 1)) {
                dp[i][j] = dp[i-1][j-1] + 1;
            } else {
                dp[i][j] = Math.max(dp[i-1][j], dp[i][j-1]);
            }
            
        }
    }
    
    // console.log(dp)
    
    return dp[text1.length][text2.length]
};