github.com/deroproject/derosuite@v2.1.6-1.0.20200307070847-0f2e589c7a2b+incompatible/p2p/median.go (about)

     1  // Copyright 2017-2018 DERO Project. All rights reserved.
     2  // Use of this source code in any form is governed by RESEARCH license.
     3  // license can be found in the LICENSE file.
     4  // GPG: 0F39 E425 8C65 3947 702A  8234 08B2 0360 A03A 9DE8
     5  //
     6  //
     7  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
     8  // EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     9  // MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
    10  // THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    11  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
    12  // PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
    13  // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
    14  // STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
    15  // THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
    16  
    17  package p2p
    18  
    19  import "sort"
    20  
    21  type uint64arr []uint64
    22  
    23  func (a uint64arr) Len() int           { return len(a) }
    24  func (a uint64arr) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
    25  func (a uint64arr) Less(i, j int) bool { return a[i] > a[j] } // we sort descending by inversing the condition
    26  
    27  // Median gets the median number in a slice of uint64 numbers
    28  // this function is used in so many checks that it should have unit tests for sure
    29  // NOTE: it will the input array
    30  
    31  func Median(inputs []uint64) (median uint64) {
    32  
    33  	// Start by sorting
    34  	sort.Sort(uint64arr(inputs))
    35  
    36  	// No math is needed if there are no numbers
    37  	// For even numbers we add the two middle numbers
    38  	// and divide by two using the mean function above
    39  	// For odd numbers we just use the middle number
    40  	l := len(inputs)
    41  	if l == 0 {
    42  		return 0
    43  	} else if l%2 == 0 {
    44  		median = (inputs[(l/2)-1] + inputs[(l/2)]) / 2
    45  	} else {
    46  		median = inputs[l/2]
    47  	}
    48  
    49  	return median
    50  }