Given a list of integers, rearrange the list such that it consists of alternating minimum-maximum elements using only list operations. The first element of the list should be minimum and the second element should be the maximum of all elements present in the list. Similarly, the third element will be the next minimum element and the fourth element is the next maximum element, and so on. Use of extra space is not permitted. Examples:
Input: [1 3 8 2 7 5 6 4] Output: [1 8 2 7 3 6 4 5] Input: [1 2 3 4 5 6 7] Output: [1 7 2 6 3 5 4] Input: [1 6 2 5 3 4] Output: [1 6 2 5 3 4]
The idea is to sort the list in ascending order first. Then we start popping elements from the end of the list and insert them into their correct position in the list. Below is the implementation of above idea –
Python
# Python program to rearrange a given # list such that it consists of alternating # minimum maximum elementsinp = []# Function to rearrange a given list such # that it consists of alternating minimum # maximum elementsdef alternateSort(): global inp # Sort the list in ascending order inp.sort() # Get index to first element of # the list it = 0 it = it + 1 i = 1 while ( i < (len(inp) + 1)/2 ): i = i + 1 # pop last element (next greatest) val = inp[-1] inp.pop() # Insert it after next minimum # element inp.insert(it, val) # Increment the pointer for next # pair it = it + 2 # Driver code# Input listinp=[ 1, 3, 8, 2, 7, 5, 6, 4 ]# Rearrange the given listalternateSort()# Print the modified listprint (inp) # This code is contributed by Arnab Kundu |
Output:
1 8 2 7 3 6 4 5
Time Complexity: O(N*logN), as we are using a sort function.
Auxiliary Space: O(1), as we are not using extra space.
Please refer complete article on Rearrange a given list such that it consists of alternating minimum maximum elements for more details!
