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Javascript Program to check if a matrix is symmetric

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  • Last Updated : 11 Jan, 2022
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A square matrix is said to be symmetric matrix if the transpose of the matrix is same as the given matrix. Symmetric matrix can be obtain by changing row to column and column to row.

Examples: 

Input : 1 2 3
        2 1 4
        3 4 3
Output : Yes

Input : 3 5 8
        3 4 7
        8 5 3
Output : No

A Simple solution is to do following. 

1) Create transpose of given matrix. 
2) Check if transpose and given matrices are same or not.  

Javascript




<script>
  
// Simple javascript code for check 
// a matrix is symmetric or not.
let  MAX = 100;
  
// Fills transpose of mat[N][N] in tr[N][N]
function transpose(mat, tr, N)
{
    for(let i = 0; i < N; i++)
        for(let j = 0; j < N; j++)
            tr[i][j] = mat[j][i];
}
  
// Returns true if mat[N][N] is
// symmetric, else false
function isSymmetric(mat, N)
{
    let tr = new Array(N);
    for(let i = 0; i < N; i++)
    {
        tr[i] = new Array(MAX);
    }
    transpose(mat, tr, N);
      
    for(let i = 0; i < N; i++)
        for(let j = 0; j < N; j++)
            if (mat[i][j] != tr[i][j])
                return false;
                  
    return true;
}
  
// Driver code
let mat = [ [ 1, 3, 5 ],
            [ 3, 2, 4 ],
            [ 5, 4, 1 ] ];
  
if (isSymmetric(mat, 3))
    document.write("Yes");
else
    document.write("No");
      
// This code is contributed by decode2207
  
</script>

Output : 

 Yes

Time Complexity : O(N x N) 
Auxiliary Space : O(N x N)

An Efficient solution to check a matrix is symmetric or not is to compare matrix elements without creating a transpose. We basically need to compare mat[i][j] with mat[j][i].  

Javascript




<script>
    // Efficient Javascript code for check a matrix is symmetric or no
      
    let MAX = 100;
    
    // Returns true if mat[N][N]
    // is symmetric, else false
    function isSymmetric(mat, N)
    {
        for (let i = 0; i < N; i++)
            for (let j = 0; j < N; j++)
                if (mat[i][j] != mat[j][i])
                    return false;
        return true;
    }
      
    let mat = [ [ 1, 3, 5 ],
               [ 3, 2, 4 ],
               [ 5, 4, 1 ] ];
    
    if (isSymmetric(mat, 3))
        document.write(  "Yes");
    else
            
        document.write("NO");
  
</script>

Output: 

Yes

Time Complexity : O(N x N) 
Auxiliary Space : O(1)

Please refer complete article on Program to check if a matrix is symmetric for more details!


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