fannkuch test

def min=100000,max=0, sum=0
def iterations = 10
iterations.times {
    def n = 10
    long t1 = System.nanoTime()
    def r = fannkuch(n)
    long t2 = System.nanoTime()
    //println("Pfannkuchen(" + n + ") = " + r)
    def t = (t2 - t1) / 1_000_000
    println "time = " + t
    if (t<min) min=t
    if (t>max) max=t
    sum+=t
}
println "time avg. ${sum/iterations} ms, -${(sum/iterations)-min},/+${max-sum/iterations}"


@CompileStatic
def fannkuch(int n) {
    int check = 0
    int[] perm = new int[n]
    int[] perm1 = new int[n]
    int[] count = new int[n]
    int[] maxPerm = new int[n]
    int maxFlipsCount = 0
    int m = n - 1

    for (int i=0;i<n;i++) {
        perm1[i] = i
    }
    int r = n

    while (true) {
        // write-out the first 30 permutations

        while (r != 1) {
            count[r - 1] = r
            r--
        }
        if (!(perm1[0] == 0 || perm1[m] == m)) {
            for (int i=0; i<n; i++) {
                perm[i] = perm1[i]
            }

            int flipsCount = 0
            int k

            while (!((k = perm[0]) == 0)) {
                int k2 = (k + 1) >> 1
                for (int i=0; i<k2; i++) {
                    int temp = perm[i]
                    perm[i] = perm[k - i]
                    perm[k - i] = temp
                }
                flipsCount++
            }

            if (flipsCount > maxFlipsCount) {
                maxFlipsCount = flipsCount
                for (int i=0; i<n; i++) {
                    maxPerm[i] = perm1[i]
                }
            }
        }

        while (true) {
            if (r == n) {
                return maxFlipsCount
            }
            int perm0 = perm1[0]
            int i = 0
            while (i < r) {
                int j = i + 1
                perm1[i] = perm1[j]
                i = j
            }
            perm1[r] = perm0

            count[r] = count[r] - 1
            if (count[r] > 0) {
                break
            }
            r++
        }
    }
}