RECURSIVE IIFE SOLUTION :DDDDD

@wallhackio What is IIFE?

@vaporeon_ a special javascript syntax that lets you declare and execute a function simultaneously :DDDDD

@vaporeon_ IT'S BEAUTIFUL 🥹

/**
 * @param {character[][]} grid
 * @return {number}
 */
var numIslands = function(grid) {
    const seen = new Set;
    const R = grid.length, C = grid[0].length;

    let count = 0;
    for (let x = 0; x < R; ++x)
        for (let y = 0; y < C; ++y)
            if (!seen.has(`${x}-${y}`) && grid[x][y] === '1')
                (function crawl(grid, x, y, seen) {
                    if (x < 0 || x >= R || y < 0 || y >= C) return;

                    const key = `${x}-${y}`;
                    if (seen.has(key)) return;
                    seen.add(key);

                    if (grid[x][y] === '0') return;

                    crawl(grid, x + 1, y, seen);
                    crawl(grid, x, y + 1, seen);
                    crawl(grid, x - 1, y, seen);
                    crawl(grid, x, y - 1, seen);
                })(grid, x, y, seen), count++;

    return count;
};

@wallhackio What kind of syntax is seen.has(`${x}-${y}`)? Looks interesting. What do the backticks ` do?

@vaporeon_ it's a neat little syntax that languages have been introducing lately to make string interpolation simpler.

Instead of String(x) + "-" + String(y) you do ${x}-{y} (I can't figure out how to add the surrounding backticks in markdown so just pretend they are there)

Python has a similar thing called "fstrings". In python it would look like f"{x}-{y}"

There are some interesting other features of the backtick strings in JavaScript that I don't use that I won't describe here.