Merge pull request #783 from ishikasinha-d/rotate-by-90

Create rotate_by_90.cpp

Author: smv1999

2D Arrays/rotate_by_90.cpp

@@ -0,0 +1,55 @@
+// Given a square matrix of size N x N. The task is to rotate it by 90 degrees in anti-clockwise direction without using any extra space.
+
+#include<bits/stdc++.h>
+#include <stdio.h>
+using namespace std;
+
+int main()
+{
+    int t; cin>>t;
+    
+    while(t--)
+    {
+        int n;
+        cin>>n;
+        int matrix[n][n];
+     
+        for(int i = 0; i < n; i++)
+        {
+            for(int j = 0; j < n; j++)
+            {
+                cin>>matrix[i][j];
+            }
+        }
+        
+    //rotating the matrix by 90 , anticlockwise        
+    // the matrix will have floor(n/2) cycles 
+    for(int i=0; i<n/2; i++)
+    {
+        //parsing through each cycle and rotating
+        for(int j=i; j< n-i-1; j++)
+        {
+            //stored current element in temporary variable temp
+            int temp= matrix[i][j];
+            
+            //shifted right element to top
+            matrix[i][j]= matrix[j][n-i-1];
+            
+            //shifted bottom element to right
+            matrix[j][n-i-1]= matrix[n-1-i][n-1-j];
+            
+            //shifted left element to bottom
+            matrix[n-1-i][n-1-j] = matrix[n-1-j][i];
+            
+            //assign temp to left
+            matrix[n-1-j][i]= temp;
+        }
+    }
+    
+    for(int i = 0; i < n; i++)
+        for(int j=0; j<n; j++)
+                cout<< matrix[i][j];
+        cout<<endl;
+    }
+    return 0;
+}