计算硬币翻转序列中的交替次数

> x <- rbinom(10,1,1/2)

> x
 [1] 0 0 0 1 1 1 1 0 1 0

> sum(diff(x)!=0)
[1] 4

> x
 [1] 0 0 0 1 1 1 1 0 1 0
> rle(x)
Run Length Encoding
  lengths: int [1:5] 3 4 1 1 1
  values : num [1:5] 0 1 0 1 0
> length(rle(x)$lengths)-1
[1] 4

sum(x[-1] != head(x, n=-1))

> x <- rbinom(1e6, 1, 0.5)
> system.time(replicate(100, sum(x[-1] != head(x, n=-1))))
   user  system elapsed 
  8.421   3.688  12.150 
> system.time(replicate(100, sum(diff(x) != 0)))
   user  system elapsed 
  9.431   4.525  14.248

variable count = 0
variable state = sequence[0]
iterate i from sequence[1] to sequence[n]
    if (state not equal sequence[i])
        state = 1 - state
        count++