Longest Common Subsequence LeetCode solution in JavaScript

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/**
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 * @param {string} text1
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 * @param {string} text2
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 * @return {number}
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 */
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let memo;
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const dp = (a, b, i, j) => {
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  if (i === 0 || j === 0) return 0;
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  if (memo[i][j] != -1) return memo[i][j];
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  if (a[i - 1] === b[j - 1]) {
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    return (memo[i][j] = 1 + dp(a, b, i - 1, j - 1));
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  } else {
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    return (memo[i][j] = Math.max(dp(a, b, i - 1, j), dp(a, b, i, j - 1)));
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  }
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};
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const bottomUp = (a, b) => {
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  for (let i = 1; i <= a.length; i++) {
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    for (let j = 1; j <= b.length; j++) {
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      if (a[i - 1] === b[j - 1]) {
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        memo[i][j] = 1 + memo[i - 1][j - 1];
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      } else {
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        memo[i][j] = Math.max(memo[i - 1][j], memo[i][j - 1]);
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      }
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    }
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  }
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  return memo[a.length][b.length];
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};
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var longestCommonSubsequence = function (text1, text2) {
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  memo = [];
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  for (let i = 0; i <= text1.length; i++) {
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    memo[i] = [];
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    for (let j = 0; j <= text2.length; j++) {
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      if (i === 0 || j === 0) memo[i][j] = 0;
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      else memo[i][j] = -1;
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    }
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  }
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  return bottomUp(text1, text2, text1.length, text2.length);
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  // return dp(text1,text2,text1.length,text2.length);
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};