Given an array arr[], the task is to rearrange the array elements by swapping adjacent elements such that no element remains at same position after swapping.
Examples:
Input: arr[] = { 1, 2, 3, 4, 5 }
Output: 2 1 5 3 4
Explanation:
Adjacent elements are swapped as follows:
(1, 2 -> 2, 1)
(3, 4, 5 -> 5, 3, 4)Input: arr[] = {1, 2, 3, 4}
Output: 2 1 4 3
Explanation:
Adjacent elements are swapped as follows:
1, 2 -> 2, 1
3, 4 -> 4, 3
Approach: The key observation in the problem is that there can be two cases for the arrays to swap the array elements:
- If length of the array is even then we can easily Swap 2 Variables without using 3rd variable for every pair of contiguous elements.
- If length of array is odd then we can do the same as above but the the last 3 elements will not form a pair, So will we can easily Swap those 3 Variables without using 4th variable.
Below is the implementation of the above approach:
C++
// C++ program for the above approach #include <bits/stdc++.h> using namespace std; // Function to print the array void print(int a[], int n) { // Loop to iterate over the // elements of array for (int i = 0; i < n; i++) cout << a[i] << " "; } // Function to swap two variables without // using the third variable void swapTwo(int& x, int& y) { // Store XOR of all in x x = x ^ y; // After this, y has value of x y = x ^ y; // After this, x has value of y x = x ^ y; } // Function to swap three variables // without using fourth variable void swapThree(int& a, int& b, int& c) { // Store XOR of all in a a = a ^ b ^ c; // After this, b has value of a b = a ^ b ^ c; // After this, c has value of b c = a ^ b ^ c; // After this, a has value of c a = a ^ b ^ c; } // Function that swaps n integers void rearrangeArray(int a[], int n) { if (n % 2 == 0) { for (int i = 0; i < n - 1; i += 2) { // Swap 2 variables without // using 3rd variable swapTwo(a[i], a[i + 1]); } } else { for (int i = 0; i < n - 3; i += 2) { // Swap 2 variables without // using 3rd variable swapTwo(a[i], a[i + 1]); } // The last 3 elements will not form // pair if n is odd // Hence, swapp 3 variables without // using 4th variable swapThree(a[n - 1], a[n - 2], a[n - 3]); } // Print the array elements print(a, n); } // Driver Code int main() { // Given array arr[] int arr[] = { 1, 2, 3, 4, 5 }; int n = sizeof(arr) / sizeof(arr[0]); // Function Call rearrangeArray(arr, n); return 0; } |
chevron_right
filter_none
Java
// Java program for the above approach import java.util.*; import java.lang.*; class GFG{ // Function to print the array static void print(int a[], int n) { // Loop to iterate over the // elements of array for(int i = 0; i < n; i++) System.out.print(a[i] + " "); } // Function to swap two variables without // using the third variable static void swapTwo(int x, int y, int[] a) { // Store XOR of all in x a[x] = a[x] ^ a[y]; // After this, y has value of x a[y] = a[x] ^ a[y]; // After this, x has value of y a[x] = a[x] ^ a[y]; } // Function to swap three variables // without using fourth variable static void swapThree(int x, int y, int z, int[] a) { // Store XOR of all in a a[x] = a[x] ^ a[y] ^ a[z]; // After this, b has value of a a[y] = a[x] ^ a[y] ^ a[z]; // After this, c has value of b a[z] = a[x] ^ a[y] ^ a[z]; // After this, a has value of c a[x] = a[x] ^ a[y] ^ a[z]; } // Function that swaps n integers static void rearrangeArray(int a[], int n) { if (n % 2 == 0) { for(int i = 0; i < n - 1; i += 2) { // Swap 2 variables without // using 3rd variable swapTwo(i, i + 1, a); } } else { for(int i = 0; i < n - 3; i += 2) { // Swap 2 variables without // using 3rd variable swapTwo(i, i + 1, a); } // The last 3 elements will not form // pair if n is odd // Hence, swapp 3 variables without // using 4th variable swapThree(n - 1, n - 2, n - 3, a); } // Print the array elements print(a, n); } // Driver code public static void main (String[] args) { // Given array arr[] int arr[] = { 1, 2, 3, 4, 5 }; int n = arr.length; // Function call rearrangeArray(arr, n); } } // This code is contributed by offbeat |
chevron_right
filter_none
Python3
# Python3 program for the above approach # Function to print the array def print1(a, n): # Loop to iterate over the # elements of array for i in range(n): print(a[i], end = " ") # Function to swap two variables without # using the third variable def swapTwo(x, y): # Store XOR of all in x x = x ^ y # After this, y has value of x y = x ^ y # After this, x has value of y x = x ^ y return x, y # Function to swap three variables # without using fourth variable def swapThree(a, b, c): # Store XOR of all in a a = a ^ b ^ c # After this, b has value of a b = a ^ b ^ c # After this, c has value of b c = a ^ b ^ c # After this, a has value of c a = a ^ b ^ c return a , b , c # Function that swaps n integers def rearrangeArray(a, n): if (n % 2 == 0): for i in range (0, n - 1, 2): # Swap 2 variables without # using 3rd variable a[i], a[i + 1] = swapTwo(a[i], a[i + 1]) else: for i in range(0, n - 3, 2): # Swap 2 variables without # using 3rd variable a[i], a[i + 1] = swapTwo(a[i], a[i + 1]) # The last 3 elements will not form # pair if n is odd # Hence, swapp 3 variables without # using 4th variable a[n - 1], a[n - 2], a[n - 3] = swapThree(a[n - 1], a[n - 2], a[n - 3]) # Print the array elements print1(a, n) # Driver Code if __name__ == "__main__": # Given array arr[] arr = [1, 2, 3, 4, 5 ] n = len(arr) # Function call rearrangeArray(arr, n) # This code is contributed by chitranayal |
chevron_right
filter_none
C#
// C# program for the above approach using System; class GFG{ // Function to print the array static void print(int []a, int n) { // Loop to iterate over the // elements of array for(int i = 0; i < n; i++) Console.Write(a[i] + " "); } // Function to swap two variables without // using the third variable static void swapTwo(ref int x, ref int y) { // Store XOR of all in x x = x ^ y; // After this, y has value of x y = x ^ y; // After this, x has value of y x = x ^ y; } // Function to swap three variables // without using fourth variable static void swapThree(ref int a, ref int b, ref int c) { // Store XOR of all in a a = a ^ b ^ c; // After this, b has value of a b = a ^ b ^ c; // After this, c has value of b c = a ^ b ^ c; // After this, a has value of c a = a ^ b ^ c; } // Function that swaps n integers static void rearrangeArray(int []a, int n) { if (n % 2 == 0) { for(int i = 0; i < n - 1; i += 2) { // Swap 2 variables without // using 3rd variable swapTwo(ref a[i], ref a[i + 1]); } } else { for(int i = 0; i < n - 3; i += 2) { // Swap 2 variables without // using 3rd variable swapTwo(ref a[i], ref a[i + 1]); } // The last 3 elements will not form // pair if n is odd // Hence, swapp 3 variables without // using 4th variable swapThree(ref a[n - 1], ref a[n - 2], ref a[n - 3]); } // Print the array elements print(a, n); } // Driver Code public static void Main(string []s) { // Given array arr[] int []arr = { 1, 2, 3, 4, 5 }; int n = arr.Length; // Function call rearrangeArray(arr, n); } } // This code is contributed by rutvik_56 |
chevron_right
filter_none
Output:
2 1 4 5 3
Time Complexity: O(N)
Auxiliary Space: O(1)
Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.
Recommended Posts:
- Shuffle a given array using Fisher–Yates shuffle Algorithm
- Form an array of distinct elements with each element as sum of an element from each array
- Maximum sum of Array formed by replacing each element with sum of adjacent elements
- Sort 1 to N by swapping adjacent elements
- Check if it is possible to sort an array with conditional swapping of adjacent allowed
- Count of right shifts for each array element to be in its sorted position
- Sum of product of each element with each element after it
- Find Array formed by adding each element of given array with largest element in new array to its left
- Check if array can be sorted by swapping pairs having GCD equal to the smallest element in the array
- Check if array can be sorted by swapping pairs with GCD of set bits count equal to that of the smallest array element
- Number of swaps to sort when only adjacent swapping allowed
- Minimum integer that can be obtained by swapping adjacent digits of different parity
- Smallest number possible by swapping adjacent even odd pairs
- Make the string lexicographically smallest and non palindromic by swapping of adjacent pair of characters
- Sort an array by swapping elements of different type specified by another array
- Maximize Array sum by swapping at most K elements with another array
- Number of shuffles required for each element to return to its initial position
- Kth array element after M replacements of array elements by XOR of adjacent pairs
- Array formed from difference of each element from the largest element in the given array
- Find just strictly greater element from first array for each element in second array
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.
