Separate Squares I

/**
 * @param {number[][]} squares
 * @return {number}
 */
var separateSquares = function (squares) {
    let lo = 0;
    let hi = 2e9;

    for (let i = 0; i < 60; i++) {
        let mid = (lo + hi) / 2;
        let diff = helper(mid, squares);

        if (diff > 0) {
            lo = mid;
        } else {
            hi = mid;
        }
    }

    return hi;
};

const helper = (line, squares) => {
    const n = squares.length;
    let aAbove = 0;
    let aBelow = 0;

    for (let i = 0; i < n; i++) {
        let x = squares[i][0], y = squares[i][1];
        let l = squares[i][2];
        let total = l * l;

        if (line <= y) {
            aAbove += total;
        } else if (line >= y + l) {
            aBelow += total;
        } else {
            let aboveHeight = (y + l) - line;
            let belowHeight = line - y;
            aAbove += l * aboveHeight;
            aBelow += l * belowHeight;
        }
    }

    return aAbove - aBelow;
};