2-D Dynamic Programming

function longestCommonSubsequence(text1: string, text2: string): number {
  const m = text1.length, n = text2.length;
  const dp: number[][] = Array.from({ length: m + 1 }, () => new Array<number>(n + 1).fill(0));
  for (let i = 1; i <= m; i++)
    for (let j = 1; j <= n; j++)
      dp[i][j] = text1[i - 1] === text2[j - 1]
        ? dp[i - 1][j - 1] + 1
        : Math.max(dp[i - 1][j], dp[i][j - 1]);
  return dp[m][n];
}

def longest_common_subsequence(text1, text2)
  m = text1.length
  n = text2.length
  dp = Array.new(m + 1) { Array.new(n + 1, 0) }
  (1..m).each do |i|
    (1..n).each do |j|
      dp[i][j] = if text1[i - 1] == text2[j - 1]
                   dp[i - 1][j - 1] + 1
                 else
                   [dp[i - 1][j], dp[i][j - 1]].max
                 end
    end
  end
  dp[m][n]
end