求逆矩阵

/**
 * Inverse of a Matrix:
 * Using Gauss-Jordan Elimination;
 * by 艾孜尔江.
 **/

#include<iostream>
using namespace std;


int main()
{
    int i = 0, j = 0, k = 0, n = 0;
    float **mat = NULL;
    float d = 0.f;
    
    cout << "How many variables? ";
    cin >> n;
    cout << endl;
    
    // Allocating memory for matrix array
    mat = new float*[2*n];
    for (i = 0; i < 2*n; ++i)
    {
        mat[i] = new float[2*n]();
    }
    
    cout << "Please enter the coefficients:" << endl;
    //Inputs the coefficients of the matrix
    for(i = 0; i < n; ++i)
    {
        for(j = 0; j < n; ++j)
        {
        	// raw major!!! 
            cin >> mat[i][j];
        }
    }
    
    cout << endl << "Input matrix:" << endl;
    for (i = 0; i < n; ++i)
    {
        for (j = 0; j < n; ++j)
        {
            cout << mat[i][j] << "\t";
        }
        cout << endl;
    }
    cout << endl;
    
    // Initializing Right-hand side to identity matrix
    for(i = 0; i < n; ++i)
    {
        for(j = 0; j < 2*n; ++j)
        {
            if(j == (i+n))
            {
                mat[i][j] = 1;
            }
        }
    }
    
    // Partial pivoting
    for(i = n; i > 1; --i)
    {
        if(mat[i-1][1] < mat[i][1])
        {
            for(j = 0; j < 2*n; ++j)
            {
                d = mat[i][j];
                mat[i][j] = mat[i-1][j];
                mat[i-1][j] = d;
            }
        }
    }
    cout << endl;
    
    // Pivoted output
    cout << "Pivoted output: " << endl;
    for(i = 0; i < n; ++i)
    {
        for(j = 0; j < 2*n; ++j)
        {
            cout << mat[i][j] << "\t";
        }
        cout << endl;
    }
    cout << endl;
    
    // Reducing To Diagonal Matrix
    for(i = 0; i < n; ++i)
    {
        for(j = 0; j < 2*n; ++j)
        {
            if(j != i)
            {
                d = mat[j][i] / mat[i][i];
                for(k = 0; k < n*2; ++k)
                {
                    mat[j][k] -= mat[i][k]*d;
                }
            }
        }
    }
    cout << endl;
    
    // Reducing To Unit Matrix
    for(i = 0; i < n; ++i)
    {
        d = mat[i][i];
        for(j = 0; j < 2*n; ++j)
        {
            mat[i][j] = mat[i][j]/d;
        }
    }
    
    // Print inverse of the input matrix
    cout<<"Inverse matrix:" << endl;
    for(i=0; i < n; ++i)
    {
        for(j = n; j < 2*n; ++j)
        {
            cout << mat[i][j] << "\t";
        }
        cout << endl;
    }
    
    // Deleting the memory allocated
    for (i = 0; i < n; ++i)
    {
        delete[] mat[i];
    }
    delete[] mat;
    
    return 0;
}

作者：艾孜尔江

__EOF__

本文作者：艾孜尔江
本文链接：https://www.cnblogs.com/ezhar/p/14190397.html
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