# Python Program for Iterative Quick Sort

 `# Python program for implementation of Quicksort  ` ` `  `# This function is same in both iterative and recursive ` `def` `partition(arr,l,h): ` `    ``i ``=` `( l ``-` `1` `) ` `    ``x ``=` `arr[h] ` ` `  `    ``for` `j ``in` `range``(l , h): ` `        ``if`   `arr[j] <``=` `x: ` ` `  `            ``# increment index of smaller element ` `            ``i ``=` `i``+``1` `            ``arr[i],arr[j] ``=` `arr[j],arr[i] ` ` `  `    ``arr[i``+``1``],arr[h] ``=` `arr[h],arr[i``+``1``] ` `    ``return` `(i``+``1``) ` ` `  `# Function to do Quick sort ` `# arr[] --> Array to be sorted, ` `# l  --> Starting index, ` `# h  --> Ending index ` `def` `quickSortIterative(arr,l,h): ` ` `  `    ``# Create an auxiliary stack ` `    ``size ``=` `h ``-` `l ``+` `1` `    ``stack ``=` `[``0``] ``*` `(size) ` ` `  `    ``# initialize top of stack ` `    ``top ``=` `-``1` ` `  `    ``# push initial values of l and h to stack ` `    ``top ``=` `top ``+` `1` `    ``stack[top] ``=` `l ` `    ``top ``=` `top ``+` `1` `    ``stack[top] ``=` `h ` ` `  `    ``# Keep popping from stack while is not empty ` `    ``while` `top >``=` `0``: ` ` `  `        ``# Pop h and l ` `        ``h ``=` `stack[top] ` `        ``top ``=` `top ``-` `1` `        ``l ``=` `stack[top] ` `        ``top ``=` `top ``-` `1` ` `  `        ``# Set pivot element at its correct position in ` `        ``# sorted array ` `        ``p ``=` `partition( arr, l, h ) ` ` `  `        ``# If there are elements on left side of pivot, ` `        ``# then push left side to stack ` `        ``if` `p``-``1` `> l: ` `            ``top ``=` `top ``+` `1` `            ``stack[top] ``=` `l ` `            ``top ``=` `top ``+` `1` `            ``stack[top] ``=` `p ``-` `1` ` `  `        ``# If there are elements on right side of pivot, ` `        ``# then push right side to stack ` `        ``if` `p``+``1` `< h: ` `            ``top ``=` `top ``+` `1` `            ``stack[top] ``=` `p ``+` `1` `            ``top ``=` `top ``+` `1` `            ``stack[top] ``=` `h ` ` `  `# Driver code to test above ` `arr ``=` `[``4``, ``3``, ``5``, ``2``, ``1``, ``3``, ``2``, ``3``] ` `n ``=` `len``(arr) ` `quickSortIterative(arr, ``0``, n``-``1``) ` `print` `(``"Sorted array is:"``) ` `for` `i ``in` `range``(n): ` `    ``print` `(``"%d"` `%``arr[i]), ` ` `  `# This code is contributed by Mohit Kumra `

Output:

```Sorted array is:
1 2 2 3 3 3 4 5
```

The above mentioned optimizations for recursive quick sort can also be applied to iterative version.

1) Partition process is same in both recursive and iterative. The same techniques to choose optimal pivot can also be applied to iterative version.

2) To reduce the stack size, first push the indexes of smaller half.

3) Use insertion sort when the size reduces below a experimentally calculated threshold.
Please refer complete article on Iterative Quick Sort for more details!

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