/**
 * @param {number} num
 * @return {boolean}
 */
var isPerfectSquare = function (num) {
    let left = 1,
        right = num;

    while (left <= right) {
        let mid = Math.floor((left + right) / 2);

        if (mid * mid === num) return true;
        else if (mid * mid > num) right = mid - 1;
        else left = mid + 1;
    }

    return false;
};