Longest Common Subsequence Between Two Strings In JavaScript

Write a solution for LCS in JavaScript (with brief explanation)

[vilayhongbounthanh]

Hi, Mono Li I saw your video and it is great solution.

[kettenbach]

Awesome solution. I love this kind of content. My mind was blown how you created the matrix with Array. from, I've never even thought of that. Thanks for sharing

[inqztiv]

Thanks for this great vid Mono! Cheers.

[monoli]

Full Code:
function lcs(str1, str2) {
let larger, smaller, largerLength, smallerLength;
if (str1.length >= str2.length) {
larger = str1;
smaller = str2;
} else {
larger = str2;
smaller = str1;
}
largerLength = larger.length;
smallerLength = smaller.length;
let matrix = Array.from({ length: smallerLength + 1 }, () =>
Array.from({ length: largerLength + 1 }, () => 0)
);
for (let row = 1; row < matrix.length; row++) {
for (let col = 1; col < matrix[row].length; col++) {
if (larger[col - 1] === smaller[row - 1]) {
matrix[row][col] = matrix[row - 1][col - 1] + 1;
} else {
matrix[row][col] = Math.max(matrix[row][col - 1], matrix[row - 1][col]);
}
}
}
let traceResult = [];
(function tracer(row, col) {
if (matrix[row][col] === 0) return;
if (matrix[row][col] === matrix[row][col - 1]) {
tracer(row, col - 1);
} else if (matrix[row][col] === matrix[row - 1][col]) {
tracer(row - 1, col);
} else if (matrix[row][col] === matrix[row - 1][col - 1] + 1) {
traceResult.push(larger[col - 1]);
tracer(row - 1, col - 1);
}
})(smallerLength, largerLength);
return
}


// console.log(lcs("BACBEDZ", "BZZZAC"))
// console.log( lcs("aaaa", "aa") )//=> "ABAD"
// lcs("AGGTAB", "GXTXAYB") => "GTAB"
// lcs("aaaa", "aa") => "aa"