Sqrt(x) II

如果x<1，那么sqrt(x)是>x的。在这种情况下我们把end设为1

public class Solution {
    /**
     * @param x a double
     * @return the square root of x
     */
    public double sqrt(double x) {
        // Write your code here
        if (x < 0) throw new IllegalArgumentException();
        double left = 0.0;
        double right = x;
        double error = 1e-12;
        if (right < 1.0) right = 1.0;
        double mid;
        while (right - left > error) {
            mid = left + (right - left) / 2;
            if (mid * mid == x) return mid;
            if (mid * mid > x) right = mid;
            else left = mid;
        }
        return left;
    }

}