Bubble sort using for loop in R

Question

I'm learning basic algorithms in R. I want to create bubble sort algorithm using for loop.

x <- c(20,31,8,46,19) 
for (i in 1:length(x)){

  if (x[i] > x[i+1]){
    temp <- x[i]
    x[i] <- x[i+1]
    x[i+1] <- temp
    cat(x[i],"")
   }
  else   cat (x[i],"")
}

I think in this particular vector, sorting should take place in three "turns.

1st should give a result: 20 8 31 19 46

2nd: 8 20 19 31 46

3rd: 8 19 20 31 46 (correct one)

This loop works out the 1st turn, except printing the last element.

I also don't know how to work out those other "turns". I predict it's something about the other for loop, but I don't know how to implement it.

Answer 1

You're iterating until the last element in x , but use x[i] > x[i+1] . So, in the last iteration x[x+1] is out of bounds. Look into this code which just deals with length(x)-1 iterations plus adds an outside loop which runs from the back to the front of the vector.

bubblesort <- function(x) {
  for (j in (length(x)-1):1) {
    for (i in j:(length(x)-1)) {
      if (x[i] > x[i+1]) {
        temp <- x[i]
        x[i] <- x[i+1]
        x[i+1] <- temp
      }
    }
  }
  return(x)
}

x <- c(20,31,8,46,19)
print(x)
print(bubblesort(x))