JS implementation of your algorithm:

const arr = [0];
for (let i = 1; i <= n; ++i) arr[i] = 0;

queries.forEach(query => {
    const [a, b, k] = query;
    arr[a] += k;
    if (b + 1 < arr.length) arr[b+1] -= k;
});

const {x, max} = arr.reduce((acc, current) => {
    acc.x += current;
    acc.max = Math.max(acc.max, acc.x);
    return acc;
}, {x: 0, max: -Infinity});

return max;