Iterative Quick Sort | An iterative implementation of quick sort ; A utility function to swap two elements ; This function is same in both iterative and recursive ; A [ ] -- > Array to be sorted , l -- > Starting index , h -- > Ending index ; Create an auxiliary stack ; initialize top of stack ; push initial values of l and h to stack ; Keep popping from stack while is not empty ; Pop h and l ; Set pivot element at its correct position in sorted array ; If there are elements on left side of pivot , then push left side to stack ; If there are elements on right side of pivot , then push right side to stack ; A utility function to print contents of arr ; Driver code ; Function calling
#include <bits/stdc++.h> NEW_LINE using namespace std ; void swap ( int * a , int * b ) { int t = * a ; * a = * b ; * b = t ; } int partition ( int arr [ ] , int l , int h ) { int x = arr [ h ] ; int i = ( l - 1 ) ; for ( int j = l ; j <= h - 1 ; j ++ ) { if ( arr [ j ] <= x ) { i ++ ; swap ( & arr [ i ] , & arr [ j ] ) ; } } swap ( & arr [ i + 1 ] , & arr [ h ] ) ; return ( i + 1 ) ; } void quickSortIterative ( int arr [ ] , int l , int h ) { int stack [ h - l + 1 ] ; int top = -1 ; stack [ ++ top ] = l ; stack [ ++ top ] = h ; while ( top >= 0 ) { h = stack [ top -- ] ; l = stack [ top -- ] ; int p = partition ( arr , l , h ) ; if ( p - 1 > l ) { stack [ ++ top ] = l ; stack [ ++ top ] = p - 1 ; } if ( p + 1 < h ) { stack [ ++ top ] = p + 1 ; stack [ ++ top ] = h ; } } } void printArr ( int arr [ ] , int n ) { int i ; for ( i = 0 ; i < n ; ++ i ) cout << arr [ i ] << " ▁ " ; } int main ( ) { int arr [ ] = { 4 , 3 , 5 , 2 , 1 , 3 , 2 , 3 } ; int n = sizeof ( arr ) / sizeof ( * arr ) ; quickSortIterative ( arr , 0 , n - 1 ) ; printArr ( arr , n ) ; return 0 ; }