#Initialization

A. Set F[k] ← k + 1 and B[k] ← k − 1, 0 ≤ k < N.

B. Set up two (FIFO) queues, Q1 and Q2, and put all the numbers, 0, …, N − 1, in order into Q1 while Q2 remains empty.

C. Define a marker variable m and a flag.

#Processing

While (Q1 nonempty){

Set m ← 0.

While (Q1 nonempty){

k ← dequeue Q1.

If(m ≤ k){

Set flag ← 0.

While (F[k] ≠ N and intervals at k and F[k] are adjacent violators){

Pool intervals beginning at k and F[k].

Set u ← F[F[k]].

Redefine F[k] ← u.

If (u < N) redefine B[u] ← k.

Update m ← u.

Update flag ← 1.

}

}

If (flag = 1 and B[k] ≥ 0) enqueue B[k] in Q2.

}

Interchange Q1 and Q2.

}