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Last active Jul 23, 2016
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Determinant of a Matrix Laplace Method
import javax.naming.OperationNotSupportedException;
import java.lang.Exception;
import java.lang.Math;
import java.lang.String;
import java.lang.System;
import java.util.Scanner;
class Matrix
{
private int mat[][];
private int n,m;
Matrix (int a[][])
{
this.mat = (int[][])a.clone();
this.n = a.length;
this.m = a[0].length;
}
public void print_mat ()
{
print_mat(mat);
}
private void print_mat (int a[][])
{
for (int i = 0; i < a.length; ++i)
{
for (int j = 0; j < a[0].length; ++j)
System.out.print(a[i][j] + " ");
System.out.print("\n");
}
}
public int determinant ()
{
if (n == m)
return determinant(mat,n);
else return 0;
}
private int[][] cofactor (int a[][], int n, int p, int q)
{
int cofac[][] = new int [n-1][n-1];
int x = 0, y = 0;
for (int i = 0; i < n; ++i)
{
for (int j = 0; j < n; ++j)
if (i != p && j != q)
{
cofac[x][y] = a[i][j];
y++;
}
if (y > n-2) { ++x; y = 0; }
}
return cofac;
}
private int determinant (int a[][], int n)
{
if (n == 1) return a[0][0];
else
{
int res = 0;
for (int i = 0; i < n; ++i)
res += ((int)Math.pow(-1, i+0)) * a[i][0] * determinant(cofactor(a, n, i, 0), n-1);
return res;
}
}
}
class RunApp
{
public static void main (String arg[])
{
Scanner readIn = new Scanner(System.in);
int n = readIn.nextInt();
int a[][] = new int[n][n];
for (int i = 0; i < n; ++i)
for (int j = 0; j < n; ++j)
a[i][j] = readIn.nextInt();
Matrix x = new Matrix(a);
//x.print_mat();
System.out.println(x.determinant());
}
}
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@suvojit-0x55aa suvojit-0x55aa commented Jul 23, 2016

//Input
3
4 5 6
8 5 6
4 5 1

//Output
100

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