模式计算

//实现求出一个数组中邻接次数最多的等值元素
import UIKit
//先使用归并算法对数组进行预排序
func MergeSort(A:[Int]) -> [Int]{
    var array = A
    if array.count < 2 {
        return array
    }
    
    let pivot = array.count / 2
    let leftArray = Array(array[0...pivot-1])
    let rightArray = Array(array[pivot...array.count-1])
    return Merge(MergeSort(leftArray),B: MergeSort(rightArray))
    
}
func Merge(A:[Int], B:[Int])->[Int]{
    var leftIndex = 0
    var rightIndex = 0
    var outputArray = [Int]()
    
    while leftIndex < A.count && rightIndex < B.count{
        if A[leftIndex] <= B[rightIndex]{
            outputArray.append(A[leftIndex])
            leftIndex = leftIndex + 1
        }else{
            outputArray.append(B[rightIndex])
            rightIndex = rightIndex + 1
        }
    }
    
    if leftIndex == A.count {
        outputArray = outputArray + B[rightIndex...B.count-1]
    }else{
        outputArray = outputArray + A[leftIndex...A.count-1]
    }
    return outputArray
}
//对预排序后的数组进行模式计算
func PresortMode(A:[Int]) -> Int {
    var modeFrequency = 0                   //目前为止求出的最高频率
    var i = 0
    var modelValue = 0
    while i <= A.count-1 {
        var runlength = 1, runvalue = A[i]
        while i + runlength <= A.count && A[i + runlength] == runvalue{
            runlength = runlength + 1
        }
        if runlength > modeFrequency{
            modeFrequency = runlength
            modelValue = runvalue
        }
        i = i + runlength
    }
    return modelValue
}
var A = [10,9,8,5,6,3,22,54,35,78,01,85,42,96,5,4,79,5,2,3,654,478,88,5,441,2,24,41,23,36,8,74,25,48,4521,1,5,57,741,32,5,7,78,5,11,23,5,6,98,8,9,87,474,68,52,14,878,55,1,55,5,454,2,52,5,45,41,2,55,9,6,5,41,74,75,5,2,2,455,5,2,14,455,5,2,21,45,54]
let B = MergeSort(A)
let ans = PresortMode(B)