dungeon.js

/**
 * @param {number[][]} dungeon
 * @return {number}
 */
var calculateMinimumHP = function(dungeon) {
    const xMax = dungeon[0].length - 1;
    const yMax = dungeon.length - 1;
    
    const hp = new Map([
        [key(xMax + 1, yMax), 1],
        [key(xMax, yMax + 1), 1]
    ]);

    for (let y = yMax; y >= 0; y--) {
        for (let x = xMax; x >= 0; x--) {
            hp.set(key(x, y), min(dungeon, x, y, hp));
        }
    }
    
    return get(hp, 0, 0);
};

function min(dungeon, x, y, hp) {
    const value = dungeon[y][x];

    return Math.max(
        1,
        Math.min(get(hp, x + 1, y), get(hp, x, y + 1)) - value,
    );
}

function get(hp, x, y) {
    return hp.get(key(x, y)) ?? Infinity;
}

function key(x, y) {
  return `${x},${y}`;
}