Determinant of a Matrix using Determinant properties

In this method, we are using the properties of Determinant.

Converting the given matrix into an upper triangular matrix using determinant properties

The determinant of the upper triangular matrix is the product of all diagonal elements.

Iterating every diagonal element and making all the elements down the diagonal as zero using determinant properties

If the diagonal element is zero then search for the next non-zero element in the same column.

There exist two cases:

Case 1: If there is no non-zero element. In this case, the determinant of a matrix is zero
Case 2: If there exists a non-zero element there exist two cases
- Case A: If the index is with a respective diagonal row element. Using the determinant properties make all the column elements down to it zero
- Case B: Swap the row with respect to the diagonal element column and continue the Case A operation.

Below is the implementation of the above approach:

C++

// C++ program to find Determinant of a matrix
#include <bits/stdc++.h>
using namespace std;
 
// Dimension of input square matrix
#define N 4
// Function to get determinant of matrix
int determinantOfMatrix(int mat[N][N], int n)
{
    int num1, num2, det = 1, index,
                    total = 1; // Initialize result
 
    // temporary array for storing row
    int temp[n + 1];
 
    // loop for traversing the diagonal elements
    for (int i = 0; i < n; i++) 
    {
        index = i; // initialize the index
 
        // finding the index which has non zero value
        while (index < n && mat[index][i] == 0) 
        {
            index++;
        }
        if (index == n) // if there is non zero element
        {
            // the determinant of matrix as zero
            continue;
        }
        if (index != i) 
        {
            // loop for swapping the diagonal element row and
            // index row
            for (int j = 0; j < n; j++) 
            {
                swap(mat[index][j], mat[i][j]);
            }
            // determinant sign changes when we shift rows
            // go through determinant properties
            det = det * pow(-1, index - i);
        }
 
        // storing the values of diagonal row elements
        for (int j = 0; j < n; j++) 
        {
            temp[j] = mat[i][j];
        }
        // traversing every row below the diagonal element
        for (int j = i + 1; j < n; j++) 
        {
            num1 = temp[i]; // value of diagonal element
            num2 = mat[j][i]; // value of next row element
 
            // traversing every column of row
            // and multiplying to every row
            for (int k = 0; k < n; k++) 
            {
                // multiplying to make the diagonal
                // element and next row element equal
                mat[j][k]
                    = (num1 * mat[j][k]) - (num2 * temp[k]);
            }
            total = total * num1; // Det(kA)=kDet(A);
        }
    }
 
    // multiplying the diagonal elements to get determinant
    for (int i = 0; i < n; i++) 
    {
        det = det * mat[i][i];
    }
    return (det / total); // Det(kA)/k=Det(A);
}
 
// Driver code
int main()
{
    /*int mat[N][N] = {{6, 1, 1},
                        {4, -2, 5},
                        {2, 8, 7}}; */
 
    int mat[N][N] = { { 1, 0, 2, -1 },
                      { 3, 0, 0, 5 },
                      { 2, 1, 4, -3 },
                      { 1, 0, 5, 0 } };
 
    // Function call
    printf("Determinant of the matrix is : %d",
           determinantOfMatrix(mat, N));
    return 0;
}

Java

// Java program to find Determinant of a matrix
class GFG 
{
 
    // Dimension of input square matrix
    static final int N = 4;
 
    // Function to get determinant of matrix
    static int determinantOfMatrix(int mat[][], int n)
    {
        int num1, num2, det = 1, index,
                        total = 1; // Initialize result
 
        // temporary array for storing row
        int[] temp = new int[n + 1];
 
        // loop for traversing the diagonal elements
        for (int i = 0; i < n; i++) 
        {
            index = i; // initialize the index
 
            // finding the index which has non zero value
            while (index < n && mat[index][i] == 0) 
            {
                index++;
            }
            if (index == n) // if there is non zero element
            {
                // the determinant of matrix as zero
                continue;
            }
            if (index != i)
            {
                // loop for swapping the diagonal element row
                // and index row
                for (int j = 0; j < n; j++)
                {
                    swap(mat, index, j, i, j);
                }
                // determinant sign changes when we shift
                // rows go through determinant properties
                det = (int)(det * Math.pow(-1, index - i));
            }
 
            // storing the values of diagonal row elements
            for (int j = 0; j < n; j++) 
            {
                temp[j] = mat[i][j];
            }
 
            // traversing every row below the diagonal
            // element
            for (int j = i + 1; j < n; j++) 
            {
                num1 = temp[i]; // value of diagonal element
                num2 = mat[j]
                          [i]; // value of next row element
 
                // traversing every column of row
                // and multiplying to every row
                for (int k = 0; k < n; k++) 
                {
                    // multiplying to make the diagonal
                    // element and next row element equal
                    mat[j][k] = (num1 * mat[j][k])
                                - (num2 * temp[k]);
                }
                total = total * num1; // Det(kA)=kDet(A);
            }
        }
 
        // multiplying the diagonal elements to get
        // determinant
        for (int i = 0; i < n; i++) 
        {
            det = det * mat[i][i];
        }
        return (det / total); // Det(kA)/k=Det(A);
    }
 
    static int[][] swap(int[][] arr, int i1, int j1, int i2,
                        int j2)
    {
        int temp = arr[i1][j1];
        arr[i1][j1] = arr[i2][j2];
        arr[i2][j2] = temp;
        return arr;
    }
 
    // Driver code
    public static void main(String[] args)
    {
        /*int mat[N][N] = {{6, 1, 1},
                        {4, -2, 5},
                        {2, 8, 7}}; */
 
        int mat[][] = { { 1, 0, 2, -1 },
                        { 3, 0, 0, 5 },
                        { 2, 1, 4, -3 },
                        { 1, 0, 5, 0 } };
 
        // Function call
        System.out.printf(
            "Determinant of the matrix is : %d",
            determinantOfMatrix(mat, N));
    }
}
 
// This code is contributed by Rajput-Ji

Python3

# Python program to find Determinant of a matrix
 
 
def determinantOfMatrix(mat, n):
 
    temp = [0]*n  # temporary array for storing row
    total = 1
    det = 1  # initialize result
 
    # loop for traversing the diagonal elements
    for i in range(0, n):
        index = i  # initialize the index
 
        # finding the index which has non zero value
        while(index < n and mat[index][i] == 0):
            index += 1
 
        if(index == n):  # if there is non zero element
            # the determinant of matrix as zero
            continue
 
        if(index != i):
            # loop for swapping the diagonal element row and index row
            for j in range(0, n):
                mat[index][j], mat[i][j] = mat[i][j], mat[index][j]
 
            # determinant sign changes when we shift rows
            # go through determinant properties
            det = det*int(pow(-1, index-i))
 
        # storing the values of diagonal row elements
        for j in range(0, n):
            temp[j] = mat[i][j]
 
        # traversing every row below the diagonal element
        for j in range(i+1, n):
            num1 = temp[i]     # value of diagonal element
            num2 = mat[j][i]   # value of next row element
 
            # traversing every column of row
            # and multiplying to every row
            for k in range(0, n):
                # multiplying to make the diagonal
                # element and next row element equal
 
                mat[j][k] = (num1*mat[j][k]) - (num2*temp[k])
 
            total = total * num1  # Det(kA)=kDet(A);
 
    # multiplying the diagonal elements to get determinant
    for i in range(0, n):
        det = det*mat[i][i]
 
    return int(det/total)  # Det(kA)/k=Det(A);
 
 
# Drivers code
if __name__ == "__main__":
    # mat=[[6 1 1][4 -2 5][2 8 7]]
 
    mat = [[1, 0, 2, -1], [3, 0, 0, 5], [2, 1, 4, -3], [1, 0, 5, 0]]
    N = len(mat)
     
    # Function call
    print("Determinant of the matrix is : ", determinantOfMatrix(mat, N))

C#

// C# program to find Determinant of a matrix
using System;
 
class GFG {
 
    // Dimension of input square matrix
    static readonly int N = 4;
 
    // Function to get determinant of matrix
    static int determinantOfMatrix(int[, ] mat, int n)
    {
        int num1, num2, det = 1, index,
                        total = 1; // Initialize result
 
        // temporary array for storing row
        int[] temp = new int[n + 1];
 
        // loop for traversing the diagonal elements
        for (int i = 0; i < n; i++)
        {
            index = i; // initialize the index
 
            // finding the index which has non zero value
            while(index < n && mat[index, i] == 0) 
            {
                index++;
            }
            if (index == n) // if there is non zero element
            {
                // the determinant of matrix as zero
                continue;
            }
            if (index != i) 
            {
                // loop for swapping the diagonal element row
                // and index row
                for (int j = 0; j < n; j++) 
                {
                    swap(mat, index, j, i, j);
                }
                // determinant sign changes when we shift
                // rows go through determinant properties
                det = (int)(det * Math.Pow(-1, index - i));
            }
 
            // storing the values of diagonal row elements
            for (int j = 0; j < n; j++)
            {
                temp[j] = mat[i, j];
            }
 
            // traversing every row below the diagonal
            // element
            for (int j = i + 1; j < n; j++) 
            {
                num1 = temp[i]; // value of diagonal element
                num2 = mat[j,
                           i]; // value of next row element
 
                // traversing every column of row
                // and multiplying to every row
                for (int k = 0; k < n; k++)
                {
 
                    // multiplying to make the diagonal
                    // element and next row element equal
                    mat[j, k] = (num1 * mat[j, k])
                                - (num2 * temp[k]);
                }
                total = total * num1; // Det(kA)=kDet(A);
            }
        }
 
        // multiplying the diagonal elements to get
        // determinant
        for (int i = 0; i < n; i++) 
        {
            det = det * mat[i, i];
        }
        return (det / total); // Det(kA)/k=Det(A);
    }
 
    static int[, ] swap(int[, ] arr, int i1, int j1, int i2,
                        int j2)
    {
        int temp = arr[i1, j1];
        arr[i1, j1] = arr[i2, j2];
        arr[i2, j2] = temp;
        return arr;
    }
 
    // Driver code
    public static void Main(String[] args)
    {
        /*int mat[N,N] = {{6, 1, 1},
                        {4, -2, 5},
                        {2, 8, 7}}; */
 
        int[, ] mat = { { 1, 0, 2, -1 },
                        { 3, 0, 0, 5 },
                        { 2, 1, 4, -3 },
                        { 1, 0, 5, 0 } };
 
        // Function call
        Console.Write("Determinant of the matrix is : {0}",
                      determinantOfMatrix(mat, N));
    }
}
 
// This code is contributed by 29AjayKumar

Javascript

Javascript<script>
// javascript program to find Determinant of a matrix
 
 
    // Dimension of input square matrix
      var N = 4;
 
    // Function to get determinant of matrix
    function determinantOfMatrix(mat , n)
    {
        var num1, num2, det = 1, index,
                        total = 1; // Initialize result
 
        // temporary array for storing row
        var temp = Array(n + 1).fill(0);
 
        // loop for traversing the diagonal elements
        for (i = 0; i < n; i++) 
        {
            index = i; // initialize the index
 
            // finding the index which has non zero value
            while (index < n && mat[index][i] == 0) 
            {
                index++;
            }
            if (index == n) // if there is non zero element
            {
                // the determinant of matrix as zero
                continue;
            }
            if (index != i)
            {
                // loop for swapping the diagonal element row
                // and index row
                for (j = 0; j < n; j++)
                {
                    swap(mat, index, j, i, j);
                }
                // determinant sign changes when we shift
                // rows go through determinant properties
                det = parseInt((det * Math.pow(-1, index - i)));
            }
 
            // storing the values of diagonal row elements
            for (j = 0; j < n; j++) 
            {
                temp[j] = mat[i][j];
            }
 
            // traversing every row below the diagonal
            // element
            for (j = i + 1; j < n; j++) 
            {
                num1 = temp[i]; // value of diagonal element
                num2 = mat[j]
                          [i]; // value of next row element
 
                // traversing every column of row
                // and multiplying to every row
                for (k = 0; k < n; k++) 
                {
                    // multiplying to make the diagonal
                    // element and next row element equal
                    mat[j][k] = (num1 * mat[j][k])
                                - (num2 * temp[k]);
                }
                total = total * num1; // Det(kA)=kDet(A);
            }
        }
 
        // multiplying the diagonal elements to get
        // determinant
        for (i = 0; i < n; i++) 
        {
            det = det * mat[i][i];
        }
        return (det / total); // Det(kA)/k=Det(A);
    }
 
     function swap(arr , i1 , j1 , i2,
                         j2)
    {
        var temp = arr[i1][j1];
        arr[i1][j1] = arr[i2][j2];
        arr[i2][j2] = temp;
        return arr;
    }
 
    // Driver code
     
 
        /*var mat[N][N] = [{6, 1, 1],
                        {4, -2, 5],
                        {2, 8, 7}]; */
 
        var mat = [ [ 1, 0, 2, -1 ],
                        [ 3, 0, 0, 5 ],
                        [ 2, 1, 4, -3 ],
                        [ 1, 0, 5, 0 ] ];
 
        // Function call
        document.write(
            "Determinant of the matrix is : ",
            determinantOfMatrix(mat, N));
 
// This code contributed by gauravrajput1 
</script>

Output

Determinant of the matrix is : 30

Time complexity: O(n³)
Auxiliary Space: O(n), Space used for storing row.

Determinant of a Matrix

The determinant of a Matrix is defined as a special number that is defined only for square matrices (matrices that have the same number of rows and columns). A determinant is used in many places in calculus and other matrices related to algebra, it actually represents the matrix in terms of a real number which can be used in solving a system of a linear equation and finding the inverse of a matrix.

Determinant of a Matrix using Determinant properties

C++

Java

Python3

C#

Javascript

Determinant of a Matrix

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Determinant of a Matrix using Determinant properties

C++

Java

Python3

C#

Javascript

Determinant of a Matrix

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Contact US