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Rotate the Matrix:

 You are given a NxN matrix.You have to rotate same coloured rectangle clockwise or anticlockwise alternatively by a ‘k’ value. K value keeps on increasing by one as we move from outer to inner loop.Suppose in the given figure outermost loop is rotated by 1 place clockwise followed by next loop rotated by 2 places anticlockwise and so on. [Give only Inplace solution].
// Picture taken from :  https://www.geeksforgeeks.org/factset-interview-experience-set-12-campus/

Solution:

#include <iostream>
using namespace std;
#define N 5

void printMatrix(int A[][N]){
    for(int i=0; i<N; i++){
        for(int j=0; j<N; j++)
            cout<<A[i][j]<<' ';
        cout<<endl;
    }    
}

void rotateMatrix(int A[][N]){
    int l = 0, r = N-1, t = 0, b = N-1;
    int k = 1;
    bool isClockwise = true;
    //iterating each ring (rectangle)
    while(l<r){
        // rotating the respective rectangle k times
        for(int c=1; c<=k; c++){
            //storing corner values of respective rectangle
            int tl = A[t][l], tr = A[t][r], bl = A[b][l], br = A[b][r];
            // if clockwise rotation is needed
            if(isClockwise){
                for(int i=r-1; i>l; i--) A[t][i+1] = A[t][i];
                for(int i=b-1; i>t; i--) A[i+1][r] = A[i][r];
                for(int i=l+1; i<r; i++) A[b][i-1] = A[b][i];
                for(int i=t+1; i<b; i++) A[i-1][l] = A[i][l];
                // now placing the stored temporary variables at correct place
                A[t][l+1] = tl;  A[t+1][r] = tr;  A[b][r-1] = br;  A[b-1][l] = bl;
            }
            // if antiClockwise rotation is needed
            else{
                for(int i=l+1; i<r; i++)  A[t][i-1] = A[t][i];
                for(int i=b-1; i>t; i--)  A[i+1][l] = A[i][l];
                for(int i=r-1; i>l; i--)  A[b][i+1] = A[b][i];
                for(int i=t+1; i<b; i++)  A[i-1][r] = A[i][r];
                // now placing the stored temporary variables at correct place
                A[t][r-1] = tr;  A[t+1][l] = tl;  A[b][l+1] = bl;  A[b-1][r] = br;
            }
        }
        // moving to inner rectangle and changing the rotation direction and
        // increasing value of k by 1
        l++;  r--;  t++;  b--;  isClockwise = !isClockwise;  k++;
    }
}

int main()
{
    int A[][N] = {
                        {  1,   2,  3,   4,  5},
                        {16, 17,18, 19,  6},
                        {15, 24, 25, 20, 7},
                        {14, 23, 22, 21, 8},
                        {13, 12, 11, 10, 9}
                      };
    cout<<"Printing before rotation:"<<endl;
    printMatrix(A);
    rotateMatrix(A);
    cout<<"Printing after rotation:"<<endl;
    printMatrix(A);
    return 0;
}
Enjoy learning.

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