/*
* File: main.cpp
* Author: Maelstrom
*
* Created on February 18, 2011, 2:25 PM
*/
#include <cstdlib>
#include <iostream>
#include <sstream>
#include <vector>
/*
* This program asks the user to enter a matrix, and then offers the user a number of operations the user can do to the matrix they
* entered. The program starts off by having the user input the dimensions of the matrix. Then, it asks for each element of the matrix. Current
* operations the user can can select are addition, subtraction, and multiplication. E.R.O will be added in the future.
*/
void add(std::vector < std::vector <double> >, int, int); //will add two matrices, one of which is a parameter.
void e_r_o(std::vector < std::vector <double> >, int, int);
void multi(std::vector < std::vector <double> >, int, int); //will multiple two matrices, one of which is a parameter.
void print(std::vector < std::vector <double> >, int, int); //prints out the matrix.
int main() {
std::cout << "Welcome to the Matrix manipulation program! This program can do a number of different mathmatical operations to matrices"
" including Gaussian elimination. ";
std::cout << "Please enter the dimensions and the elements of the matrix. Once completed"
", you will be given a number of mathmatical operations that can be applied to the matrix. "
"Note: if you wish to find the solutions to a linear system, make sure to include what the equations are equal to." << '\n';
int column, row; //for dimensions of the mxn matrix.
std::string input; //used to store all input.
while (true) { //infinite loop, will on be exited out of when user enters appropriate info.
std::cout << "Enter the number of rows for the matrix: "; //asks for # of rows.
std::getline(std::cin, input); //takes input as a string
std::stringstream convert(input); //enters string into the stringstream.
if (convert >> row) { //checks if the input can be converted into a double. If it can, it enters the number into row.
if (row != 0) { //can't go having a matrix with 0 rows
break; //exits out of loop.
}
}
std::cout << "Error, please enter an appropriate number of rows." << '\n';
}
while (true) { //does the same as above, but for the number of columns.
std::cout << "Enter the number of columns for the matrix: ";
std::getline(std::cin, input);
std::stringstream convert(input);
if (convert >> column) {
if (column != 0) {
break;
}
}
std::cout << "Error, please enter an appropriate number of columns." << '\n';
}
std::vector <std::vector <double> > matrix; //creates a multidimensional vector. Used instead of an array for ease of parameterizing.
matrix.resize(row);
for (int i = 0; i < row; ++i) {
matrix[i].resize(column);
} //makes the vector the desired size by using .resize
std::cout << "Please enter each element for the row." << '\n';
int r = 0;
while (r < row) { //asks user for the elements in each row of the matrix. Will repeat while r < row.
int c = 0;
std::cout << "Row " << r + 1 << ": ";
std::getline(std::cin, input);
std::stringstream convert(input);
while (true) { //loops indefinately, until each element has a double.
if (convert >> matrix[r][c]) { //checks to see if input can be converted into a double
++c; //moves to next column
}
else {
break;
}
if (c == column) { //once the last column has a double, will break out of while loop.
++r; //moves to next row
break;
}
}
}
while (true) { //asks user to select which operation they would like to do to the matrix.
std::cout << "Select which operation you would like to use on the matrix. " << '\n';
std::cout << "0) Print matrix" << '\n';
std::cout << "1) Matrix addition and subtraction" << '\n';
std::cout << "2) Matrix multiplication" << '\n';
std::cout << "3) Gaussian elimination" << '\n';
std::cout << "Selection? ";
std::getline(std::cin, input);
std::stringstream convert(input);
int selection;
if (convert >> selection) {
if (selection == 0) { //allows user to print their matrix in all its glory!
print(matrix, row, column);
break;
}
else if (selection == 1) {
add(matrix, row, column); //calls the add function, which will add to user inputed matrices.
break; //breaks out of infite while loop.
}
else if (selection ==2 ) {
multi(matrix, row, column);
break;
}
else if (selection == 3) {
e_r_o(matrix, row, column);
break;
}
}
std::cout << "Please enter an appropriate selection." << '\n';
}
std::cout << "Would you like to rerun the program?" << std::endl; //gives user the option to rerun program by using recursion.
std::cout << "Y/N? ";
std::getline(std::cin, input);
if (input == "y" || input == "Y") {
return main();
}
return 0;
}
/*
* Allows for the addition and subtraction, based on user choice, of two matrices. The first one is taken from the main, along with
* the row and column length of the first matrix. Using a multidimensional vector, a second matrix is made with the same dimensions
* as the first matrix. User is then asked to input each element. Finally, the matrices are either added or subtracted, and then
* the result is printed out, using the print function.
*/
void add(std::vector < std::vector <double> > nom, int row, int column) {
std::cout << "Please enter the elements for the row. Note: in order to add or subtract matrices, the dimensions of both must be the same."
" The dimensions of the first matrix you entered will be used for this one." << '\n';
//using same method to acquire details of second matrix.
std::string input;
std::vector <std::vector <double> > nom2;
nom2.resize(row);
for (int i = 0; i < row; ++i) {
nom2[i].resize(column);
}
int r = 0;
while (r < row) {
int c = 0;
std::cout << "Row " << r+1 << ": ";
std::getline(std::cin, input);
std::stringstream convert(input);
while (true) {
if (convert >> nom2[r][c]) {
++c;
}
else {
break;
}
if (c == column) {
++r;
break;
}
}
}
std::cout << "Addition or subtraction? "; //user can chose to add or subtract.
std::getline(std::cin, input);
if (input == "Add" || input == "add" || input == "Addition" || input == "addition") {
for (int i = 0; i < row; ++i) {
for (int j = 0; j < column; ++j) {
nom [i][j] += nom2 [i][j]; //adds each corresponding element of the two matrices together. Goes row by row.
}
}
print(nom, row, column);
}
else if (input == "Subtract" || input == "subtract" || input == "Subtraction" || input == "subtraction") {
for (int i = 0; i < row; ++i) {
for (int j = 0; j < column; ++j) {
nom [i][j] -= nom2 [i][j]; //same as above, just with subtraction.
}
}
print(nom, row, column);
}
else {
std::cout << "Please choose to add or subtract." << '\n';
}
}
/*
* Uses Gaussian-Jordan elimination to put the matrix into the reduced row-echelon form. It then prints out the matrix.
*/
void e_r_o(std::vector < std::vector <double> > nom, int row, int column) {
//puts the matrix into row-echelon form.
int a = 0, b = 0, c = 1;
while (a < row - 1) {
if (nom [a][b] != 0) {
int y = 0;
std::vector <double> holder;
holder.resize(row - 1);
for (int i = c; i < row; ++i) {
holder [y] = (nom [i][b]) / (nom [a][b]);
++y;
}
int z = 0;
for (int i = c; i < row; ++i) {
for (int j = b; j < column; ++j) {
nom [i][j] -= holder [z] * nom [a][j];
}
++z;
}
}
++a;
++b;
++c;
}
//makes leading element for each row a leading one.
for (int i = 0; i < row; ++i) {
double k = nom [i][i];
for (int j = 0; j < column; ++j) {
nom [i][j] /= k;
}
}
//makes the row-echelon formed matrix into a reduced row-echelon form.
int d = row - 1, e = column - 2, f = row - 2;
while (d > 0) {
if (nom [d][e] != 0) {
int y = 0;
std::vector <double> holder;
holder.resize(row - 1);
for (int i = f; i > -1; --i) {
holder [y] = (nom [i][e]) / (nom [d][e]);
++y;
}
int z = 0;
for (int i = f; i > -1; --i) {
for (int j = (column - 1); j > -1; --j) {
nom [i][j] -= holder [z] * nom [d][j];
}
++z;
}
}
--d;
--e;
--f;
}
print (nom, row, column);
}
/*
* Multiplies two matrices together, and then prints out the product. Gets the first matrix from the parameter, and the second
* is created by the user.
*/
void multi(std::vector < std::vector <double> > nom, int row1, int column1) {
std::cout << "Please enter the dimensions of the second matrix. Note: The number of columns of the first matrix must "
"equal the number of rows of the second matrix." << '\n';
std::string input;
int row2, column2;
while (true) { //asks for number of rows. Checks to make sure it equals the number of columns in the first matrix.
std::cout << "Number of rows (must be same as number of columns of first matrix!): ";
std::getline(std::cin, input);
std::stringstream convert (input);
if (convert >> row2) {
if (row2 == column1) {
break;
}
}
std::cout << "Please enter an appropriate value." << '\n';
}
while (true) { //asks for number of columns.
std::cout << "Number of columns: ";
std::getline(std::cin, input);
std::stringstream convert (input);
if (convert >> column2) {
if (column2 != 0) {
break;
}
}
std::cout << "Please enter an appropriate value." << '\n';
}
std::vector < std::vector <double> > nom2; //creates the second matrix based off the entered dimensions.
nom2.resize(row2);
for (int i = 0; i < row2; ++i) {
nom2[i].resize(column2);
}
std::cout << "Please enter the elements for each row." << '\n';
int r = 0;
while (r < row2) { //User enters each element for each row. Has checks in place to make sure user enters doubles.
int c = 0;
std::cout << "Row " << r+1 << ": ";
std::getline(std::cin, input);
std::stringstream convert(input);
while (true) {
if (convert >> nom2[r][c]) {
++c;
}
else {
break;
}
if (c == column2) {
++r;
break;
}
}
}
std::vector < std::vector <double> > nom3; //creates a third matrix to hold of the values of other two matrices multiplied.
nom3.resize(row1); //has row1 rows, and column 2 columns.
for (int i = 0; i < row1; ++i) {
nom3[i].resize(column2);
}
/*
* Algorithm for multiplying the two matrices. Multiples the corresponding element of the ith row of the 1st matrix and jth column
* of the 2nd matrix. Adds them together, and places the final number into the a(i,j) element of the product matrix.
*/
int z = 0;
while (z < row1) { //Z is used to track the row number for the 3rd and 1st matrix. Stops once it equals row1.
for (int a = 0; a < column2; ++a) { //Used to track the column of the 3rd and 2nd matrix. Stops once it equals column2.
for (int b = 0; b < row2; ++b) { //Used to track the column for the 1st matrix, and the row for the 2nd matrix.
nom3[z][a] += nom[z][b] * nom2[b][a]; //Multiplies the elements together, then adds the product to the corresponding element in nom3.
}
}
++z;
}
print(nom3, row1, column2);
}
/*
* Prints each element of the matrix.
*/
void print(std::vector < std::vector <double> > nom, int row, int column) {
for (int i = 0; i < row; ++i) {
for (int j = 0; j < column; ++j) {
std::cout << nom[i][j] << " ";
}
std::cout << std::endl;
}
}
. It's lots of fun, plus I am learning a good deal too. Once I have some time I'll sit down and work on some of the projects y'all suggested (spring break/summer). Damn college and its work, shouldn't it know by now that college is for fun and goofing off 
Originally.. It was just to learn new ideas AND was never really meant to finish it.. 55% or so percent later.. LOL.. I think I will eventually finish it
Granted.. all are written in Visual Basic 2007 but I could of done it in C++,Java, or C#..BUT VB is so much faster and VB is my love. I'm at the point now, it's what I call.. "Perpetual Learning"..
)
