[算法]：二分法-开方

# 二分法 逼近求开方
def square(x):
    if x > 1:
        high = x
        low = 1
    elif 0 < x < 1:
        high = 1
        low = x
    elif x == 1 or x == 0:
        return x
    else:
        return -1 * square(-1 * x)
    ACCURACY = 0.0001
    while low < high:
        mid = (high + low) / 2.0
        print 'mid = %s,low=%s,high = %s' % (mid, low, high)
        if mid*mid > x:
            high = mid
        else:
            low = mid
        if ACCURACY * -1 <= mid*mid - x <= ACCURACY:
            return float("%.4f" % mid)