Im having a problem to understand this algorithm, how would you describe it, mostly the while loops. I understand that this i an iterative function, and the use of Hoare partition scheme. But what does the while loops do, and why does it use breaks.
def inplace_quick_sort_nonrecursive(S):
if len(S) < 2:
return S
stack = [] #initialize the stack
stack.append([0, len(S) - 1])
while len(stack) > 0: #loop till the stack is empty
low, high = stack.pop() #pop low and high indexes
pivot = S[(low + high) // 2] #create pivot, of any S[] except S[high]
i = low - 1 #Hoare partition
j = high + 1
while True:
while True: #while (S[++i] < pivot)
i += 1
if(S[i] >= pivot):
break
while True: #while(S[--j] < p)
j -= 1
if(S[j] <= pivot):
break
if (i >= j): #if indexes met or crossed, break
break
S[i], S[j] = S[j], S[i] #else swap the elements
if (j > low): #push the indexes into the stack
stack.append([low, j])
j += 1
if (high > j):
stack.append([j, high])
