Question

There are a number of students standing in a single file line. Each student is numbered sequentially from 0. Each student also has a binary digit associated with them, where 0 indicate the student's performance is above average and 1 indicates the student's performance is below average.

The teacher wants to groupe the sudent by performance opposite ends of the line such that the number of adjacent pairs of students where one student is a 0 and the other student is a 1 minimized. To accomplish this, any student can swap places in line with the student located immediately in front of or behind them. Each time a pair of student swap places, it counts as a move. Determine the minimum number of moves needed to create and optimal configuration.

For example, there are n=4 students arranged as avg=[0,1,0,1]. With 1 move, switching students 1 and 2, we get the array [0,0,1,1] which is optimal.

Function Description:

Complete the function MinMoves in the editor below. The function must return an integer denoting the minimum number of moves necessary to achieve an optimal configuration.

minMoves has the following parameter(s):

avg[avg[0],....avg[n-1]]: an array of binary digits

Constraints:

1 ≤ n ≤ 10^5

avg[i] E {0,1)

PLEASE HELP...DONE IN C++

Answer 1

//For any queries, feel free to comment.

**LOGIC**

To make sure that number of adjacent pairs of students where one student is a 0 and the other student is a 1 minimized, we have to arrange students of same type together.

So possible configurations of array can be ......

[All zeros][All ones]

[All ones][All zeros]

We will have to find answer for both the cases and return the minimum of that answer.

To find answer of each configuration, we know that number_of_moves is equal to number_of_ones present in that desired zero's area (because we have to remove that number of ones).

For more explaination, see the code below.

**CODE START**

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

int minMoves(int arr[],int n){

    //Count the number of zeroes
    int cnt_zero = 0;
    for(int i=0;i<n;i++){
        if(arr[i]==0)
            cnt_zero++;
    }

    int moves,cnt = 0,ans = n;

    //Calculating no_moves when all zero are in the beginning
    //Checking first cnt_zero number of elements for 0
    moves = 0;
    for(int i=0;i<cnt_zero;i++){
        if(arr[i]!=0){
            moves++;
        }
    }

    //Updating answer
    ans = min(ans,moves);

    //Calculating no_moves when all zero are in the end
    //Checking last cnt_zero number of elements for 0
    moves = 0;
    for(int i=n-1;cnt<cnt_zero;i--,cnt++){
        if(arr[i]!=0){
            moves++;
        }
    }

    //Updating answer
    ans = min(ans,moves);

    return ans;
}

int main(){

    //n = number of elements in array
    int n;
    cin>>n;

    //Taking array input from user
    int arr[n];
    for(int i=0;i<n;i++)
        cin>>arr[i];

    //Calling function for desired answer
    cout<<minMoves(arr,n);
    return 0;
}

**CODE END**

**OUTPUT**

**SNIPPET END**