Program to check idempotent matrix

Given a N * N matrix and the task is to check matrix is idempotent matrix or not.

Idempotent matrix: A matrix is said to be idempotent matrix if matrix multiplied by itself return the same matrix. The matrix M is said to be idempotent matrix if and only if M * M = M. In idempotent matrix M is a square matrix.

Examples:

```Input : mat[][] = {{3, -6},
{1, -2}};
Output : Idempotent Matrix

Input : mat[N][N] = {{2, -2, -4},
{-1, 3, 4},
{1, -2, -3}}
Output : Idempotent Matrix.```

Implementation:

C++

 `// Program to check given matrix ` `// is idempotent matrix or not.` `#include` `#define N 3` `using` `namespace` `std;`   `// Function for matrix multiplication.` `void` `multiply(``int` `mat[][N], ``int` `res[][N])` `{` `    ``for` `(``int` `i = 0; i < N; i++)` `    ``{` `        ``for` `(``int` `j = 0; j < N; j++)` `        ``{` `            ``res[i][j] = 0;` `            ``for` `(``int` `k = 0; k < N; k++)` `                ``res[i][j] += mat[i][k] * mat[k][j];` `        ``}` `    ``}` `}`   `// Function to check idempotent` `// property of matrix.` `bool` `checkIdempotent(``int` `mat[][N])` `{   ` `    ``// Calculate multiplication of matrix` `    ``// with itself and store it into res.` `    ``int` `res[N][N];` `    ``multiply(mat, res);`   `    ``for` `(``int` `i = 0; i < N; i++)    ` `        ``for` `(``int` `j = 0; j < N; j++)        ` `            ``if` `(mat[i][j] != res[i][j])` `                ``return` `false``;` `    ``return` `true``;` `}`   `// Driver function.` `int` `main()` `{` `    ``int` `mat[N][N] = {{2, -2, -4},` `                    ``{-1, 3, 4},` `                    ``{1, -2, -3}};` `    `  `    ``// checkIdempotent function call.` `    ``if` `(checkIdempotent(mat))` `        ``cout << ``"Idempotent Matrix"``;` `    ``else` `        ``cout << ``"Not Idempotent Matrix."``;` `    ``return` `0;` `}`

Java

 `// Java program to check given matrix ` `// is idempotent matrix or not.` `import` `java.io.*;`   `class` `GFG ` `{` `    ``static` `int` `N = ``3``;` `    `  `    ``// Function for matrix multiplication.` `    ``static` `void` `multiply(``int` `mat[][], ``int` `res[][])` `    ``{` `        ``for` `(``int` `i = ``0``; i < N; i++)` `        ``{` `            ``for` `(``int` `j = ``0``; j < N; j++)` `            ``{` `                ``res[i][j] = ``0``;` `                ``for` `(``int` `k = ``0``; k < N; k++)` `                    ``res[i][j] += mat[i][k] * mat[k][j];` `            ``}` `        ``}` `    ``}` `    `  `    ``// Function to check idempotent` `    ``// property of matrix.` `    ``static` `boolean` `checkIdempotent(``int` `mat[][])` `    ``{ ` `        ``// Calculate multiplication of matrix` `        ``// with itself and store it into res.` `        ``int` `res[][] = ``new` `int``[N][N];` `        ``multiply(mat, res);` `    `  `        ``for` `(``int` `i = ``0``; i < N; i++)` `        ``{ ` `            ``for` `(``int` `j = ``0``; j < N; j++)` `            ``{` `                ``if` `(mat[i][j] != res[i][j])` `                    ``return` `false``;` `            ``}` `        ``}` `        ``return` `true``;` `    ``}`   `    ``// Driver code.` `    ``public` `static` `void` `main (String[] args) ` `    ``{` `        ``int` `mat[][] = {{``2``, -``2``, -``4``},` `                       ``{-``1``, ``3``, ``4``},` `                       ``{``1``, -``2``, -``3``}};` `    `  `        ``// checkIdempotent function call.` `        ``if` `(checkIdempotent(mat))` `            ``System.out.println( ``"Idempotent Matrix"``);` `        ``else` `            ``System.out.println(``"Not Idempotent Matrix."``);` `        `  `    ``}` `}`   `// This code is contributed by vt_m.`

Python 3

 `# Python Program to check given matrix ` `# is idempotent matrix or not.` `import` `math`   `# Function for matrix multiplication.` `def` `multiply(mat, res):`   `    ``N``=` `len``(mat)` `    ``for` `i ``in` `range``(``0``,N):` `    `  `        ``for` `j ``in` `range``(``0``,N):` `        `  `            ``res[i][j] ``=` `0` `            ``for` `k ``in` `range``(``0``,N):` `                ``res[i][j] ``+``=` `mat[i][k] ``*` `mat[k][j]`   `# Function to check idempotent` `# property of matrix.` `def` `checkIdempotent(mat):`   `    ``N``=` `len``(mat)` `    ``# Calculate multiplication of matrix` `    ``# with itself and store it into res.` `    ``res ``=``[[``0``]``*``N ``for` `i ``in` `range``(``0``,N)]` `    ``multiply(mat, res)`   `    ``for` `i ``in` `range``(``0``,N):` `        ``for` `j ``in` `range``(``0``,N):     ` `            ``if` `(mat[i][j] !``=` `res[i][j]):` `                ``return` `False` `    ``return` `True`   `# driver Function` `mat ``=` `[ [``2``, ``-``2``, ``-``4``],` `        ``[``-``1``, ``3``, ``4``],` `        ``[``1``, ``-``2``, ``-``3``] ]` `    `  `# checkIdempotent function call.` `if` `(checkIdempotent(mat)):` `    ``print``(``"Idempotent Matrix"``)` `else``:` `    ``print``(``"Not Idempotent Matrix."``)`   `# This code is contributed by Gitanjali.`

C#

 `// C# program to check given matrix ` `// is idempotent matrix or not.` `using` `System;`   `class` `GFG ` `{` `    ``static` `int` `N = 3;` `    `  `    ``// Function for matrix multiplication.` `    ``static` `void` `multiply(``int` `[,]mat, ``int` `[,]res)` `    ``{` `        ``for` `(``int` `i = 0; i < N; i++)` `        ``{` `            ``for` `(``int` `j = 0; j < N; j++)` `            ``{` `                ``res[i,j] = 0;` `                ``for` `(``int` `k = 0; k < N; k++)` `                    ``res[i,j] += mat[i,k] * mat[k,j];` `            ``}` `        ``}` `    ``}` `    `  `    ``// Function to check idempotent` `    ``// property of matrix.` `    ``static` `bool` `checkIdempotent(``int` `[,]mat)` `    ``{ ` `        ``// Calculate multiplication of matrix` `        ``// with itself and store it into res.` `        ``int` `[,]res = ``new` `int``[N,N];` `        ``multiply(mat, res);` `    `  `        ``for` `(``int` `i = 0; i < N; i++)` `        ``{ ` `            ``for` `(``int` `j = 0; j < N; j++)` `            ``{` `                ``if` `(mat[i,j] != res[i,j])` `                    ``return` `false``;` `            ``}` `        ``}` `        ``return` `true``;` `    ``}`   `    ``// Driver code` `    ``public` `static` `void` `Main () ` `    ``{` `        ``int` `[,]mat = {{2, -2, 4},` `                    ``{-1, 3, 4},` `                    ``{1, -2, -3}};` `    `  `        ``// checkIdempotent function call.` `        ``if` `(checkIdempotent(mat))` `            ``Console.WriteLine( ``"Idempotent Matrix"``);` `        ``else` `            ``Console.WriteLine(``"Not Idempotent Matrix."``);` `        `  `    ``}` `}`   `// This code is contributed by vt_m.`

Javascript

 ``

Output

`Idempotent Matrix`

Time Complexity: O(n3)
Auxiliary Space: O(n2), since n2 extra space has been taken.

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