README.md

I just use Math.pow indolently, maybe it's better to use a kind of binary if you are having an interview.

Let's see. If n is positive, it's quite simple to write down following code:

var ans = 1;
while (n) {
  (n & 1) && (ans *= x);
  x *= x;
  n >>= 1;
}

return ans;

But we should consider about the situation when n is negative, after thinking, we do this:

var myPow = function(x, n) {
  var isNegative = n < 0 ? (n *= -1, true) : false;

  var ans = 1;
  while (n) {
    (n & 1) && (ans *= x);
    x *= x;
    n >>= 1;
  }

  return isNegative ? 1 / ans : ans;
};

But it still fails, for we forget this situation when n === 2147483648, and n >> 1 will get -1073741824, so we should use / 2 or >>> instead.

var myPow = function(x, n) {
  var isNegative = n < 0 ? (n *= -1, true) : false;

  var ans = 1;
  while (n) {
    (n & 1) && (ans *= x);
    x *= x;
    n >>>= 1;
  }

  return isNegative ? 1 / ans : ans;
};