Java sqr sqrt_long(final long x)

Description

sqrlong

License

Apache License

Return

integer square root

Declaration

public static long sqrt_long(final long x) 

Method Source Code

//package com.java2s;
/**/*from   w w  w.j  a va 2s . c o  m*/
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

public class Main {
    /** @return integer square root */
    public static long sqrt_long(final long x) {
        if (x == 0)
            return 0;
        else if (x < 0)
            throw new ArithmeticException("sqrt(" + x + ")");

        final int half_nBits = (Long.SIZE - Long.numberOfLeadingZeros(x)) >> 1;
        long upper;
        long lower;
        {
            final long mid = x >> half_nBits;
            final long r = x - mid * mid;
            if (r >= 0 && r <= (mid << 1)) {
                return mid;
            } else if (r > 0) {
                upper = x >> (half_nBits - 1);
                lower = mid;
            } else {
                upper = mid;
                lower = x >> (half_nBits + 1);
            }
        }

        for (; upper - lower > 1;) {
            final long mid = (upper + lower) >> 1;
            final long r = x - mid * mid;
            if (r >= 0 && r <= (mid << 1)) {
                return mid;
            } else if (r > 0) {
                lower = mid;
            } else {
                upper = mid;
            }
        }
        return lower;
    }
}

Related

1. sqrt(short value)
2. sqrt2(float x)
3. sqrt2sq(double x, double y)
4. sqrt_double(double d)
5. sqrt_float(float value)
6. sqrtInt(Integer num)