rearrange array alternatively.cpp

/*
///////////////////////////////////////////
//Question/Info

Rearrange Array Alternately
Medium Accuracy: 50.0% Submissions: 25450 Points: 4
Given a sorted array of positive integers. Your task is to rearrange  the array elements alternatively i.e first element should be max value, second should be min value, third should be second max, fourth should be second min and so on.

Example 1:

Input:
N = 6
arr[] = {1,2,3,4,5,6}
Output: 6 1 5 2 4 3
Explanation: Max element = 6, min = 1,
second max = 5, second min = 2, and
so on... Modified array is : 6 1 5 2 4 3.
Example 2:

Input:
N = 11
arr[]={10,20,30,40,50,60,70,80,90,100,110}
Output:110 10 100 20 90 30 80 40 70 50 60
Explanation: Max element = 110, min = 10,
second max = 100, second min = 20, and
so on... Modified array is :
110 10 100 20 90 30 80 40 70 50 60.
Your Task:
The task is to complete the function rearrange() which rearranges elements as explained above. Printing of the modified array will be handled by driver code.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(1).

Constraints:
1 <= N <= 107
1 <= arr[i] <= 107

Company Tags
 Zoho

author: srj_v
///////////////////////////////////////////
*/

#include <bits/stdc++.h>
using namespace std;

// #define int 		   long long int
#define sbit(x) 	   __builtin_popcount(x)
#define pb(x) 		   push_back(x)
#define mp(x,y) 	   make_pair(x,y)
#define eb(x) 		   emplace_back(x)
#define ct(x) 		   cout << x << "\n";
#define ct2(x,y) 	   cout << x << " " << y << "\n";
#define tc(x) 		   cout << x << " ";
#define tc2(x,y) 	   cout << x << " " << y << " ";
#define forn(i,n) 	   for(int i = 0; i < (int)(n); ++i)
#define forx(i,x,n)    for(int i = x; i < (int)(n); ++i)
#define nfor(i,n)      for(int i = n-1; i >= 0; --i)
#define all(v) 		   v.begin(),v.end()
#define fsp(x,y)       fixed << setprecision(y) << x
#define PI 			   3.1415926535897932384626433832795
#define MOD 		   1000000007 // (1e9+7)
#define pii 		   pair<int,int>
#define pis 		   pair<int,string>
#define vi  		   vector<int>
#define vii 		   vector<pii>
#define mii 		   map<int,int>
#define p_q            priority_queue // priority_queue<int> (&) priority_queue< int,vi,greater<int> >
#define _IOS      	   ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

typedef long double ld;
typedef long long int lli;

#pragma GCC optimize("Ofast")

void c_p_c()
{
#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#endif
}


int32_t main() {
///////////
	c_p_c();
///////////
	_IOS
//////////

	// code

	/*
	int t ; cin >> t; while(t--){}
	*/


	class Solution {
	public:
		// This function wants you to modify the given input
		// array and no need to return anything
		// arr: input array
		// n: size of array
		//Function to rearrange  the array elements alternately.
		void rearrange(long long *arr, int n)
		{

			// Your code here

			// maximum element
			int max_idx = n - 1, min_idx = 0;

			// store maximum element of array
			int max_elem = arr[n - 1] + 1;

			// traverse array elements
			for (int i = 0; i < n; i++) {
				// at even index : we have to put maximum element
				if (i % 2 == 0) {
					arr[i] += (arr[max_idx] % max_elem) * max_elem;
					max_idx--;
				}

				// at odd index : we have to put minimum element
				else {
					arr[i] += (arr[min_idx] % max_elem) * max_elem;
					min_idx++;
				}
			}

			// array elements back to it's original form
			for (int i = 0; i < n; i++)
				arr[i] = arr[i] / max_elem;


		}
	};



// cerr << "time: " << clock() << " ms" << '\n';
	return 0;
}