// This C program provides a skeleton for a FINITE ELEMENTS METHOD
// Author (anonymous)
// Date   27.11.2007
// For    Assignment 4 for Computer Programming, Ajou University
//---------------------------------------------------------------------------
//Libraries used by this program
#include <stdio.h>     //Handles the keyboard input and screen output
#include <process.h>   //Handles DOS system commands ("cls", "pause")
#include <time.h>      //Handles date and time standard functions
#include <stdlib.h>	   //Handles (among other things) the atoi() function

//Here are "function prototypes" for all 6 functions used by this program:
void matrix_display(void);  //displays matrix
void matrix_input(void);	//allows user to input matrix
void matrix_update(void);	//dummy function
void matrix_generate(void);	//dummy function
void matrix_resolve(void);	//solves matrix
void date_and_time(void);	//retrieves date from the system


//Here is the "main" function (module)
void main() 
{
   //Local variables initiated here
   int reply=0;			//Reply with the menu choice
   int reply_sub=0;		//Reply with the submenu choice	
   int i=44, j=88; //Loop counter, loop limit
   
   //This part displays the menu items
   system("cls");	//clears screen
   printf("Welcome to MATRIX program!"); //prints welcome message
   date_and_time(); //call to function
   while (reply < 6)
   {
		printf("\n\nThis program works with matrices!\n");
        printf("\nHere are menu options that this program offers:\n");
        //This part displays menu options
             printf ("\n%d. Display", 1);	//menu choice 1
             printf ("\n%d. Input", 2);		//menu choice 2
             printf ("\n%d. Update", 3);	//menu choice 3
			 printf ("\n%d. Generate", 4);	//menu choice 4
			 printf ("\n%d. Resolve", 5);	//menu choice 5
        printf ("\n6. (or 7, ..., etc.) EXIT program."); //menu choice 6
        printf ("\n");      // Changes the line
        printf("\nTo terminate choose the option 6 or higher!"); 
        printf("\nPlease choose the item to run (e.g. 1, ..., 6) ");
        scanf("%d", &reply);  // Inputs your reply
        printf("\nYour choice was option number %d", reply); 
		printf("\n");
        //Completes the processing for subsequent options
        if (reply == 1)  // if user chose option 1 this part of program is executed
        {
			matrix_display(); //Call to the function
			system("pause");    // DOS "Pause" command (for user to look at results)
        }

         if (reply == 2) //if user chose option 2 this part of program is executed
        {
            matrix_input(); //Call to the function
			system("pause");    // DOS "Pause" command (for user to look at results)
		}

        if (reply == 3) //if user chose option 3 this part of program is executed
        {
			matrix_update(); //Call to the function
			system("pause");    // DOS "Pause" command (for user to look at results)
		}
           
		if (reply == 4) //if user chose option 3 this part of program is executed
        {
			matrix_generate(); //Call to the function
			system("pause");    // DOS "Pause" command (for user to look at results)
		}

		if (reply == 5) //if user chose option 3 this part of program is executed
        {
			matrix_resolve(); //Call to the function
			system("pause");    // DOS "Pause" command (for user to look at results)
		}

        if (reply >= 6)
        {
                //This completes actions for the option PROGRAM EXIT
                printf (" which terminates this program!");
        }
   }
   //The final displays
   printf ("\n\nThank you for using this program. Goodbye!");
   printf ("\n");      // Changes the line
   system("pause");    // DOS "Pause" command (for user to look at results)
}  //End of "main"


void date_and_time()
{
	char date_string [9]; //stores the retrieved date and time
	int year_pc = 01;        // stores the retrieved year in integer form
	int month_pc = 01;       // stores the retrieved month in integer form
	int day_pc = 01;         //stores the retrieved day in integer form

	_strdate (date_string); //This retrieves the current date
	day_pc = (date_string[3] -48)*10 + (date_string[4] - 48)*1;  // converts day
	month_pc = (date_string[0] -48)*10 + (date_string[1] -48)*1; // converts month
	year_pc = ((date_string[6] -48)*10 +(date_string[7] -48)*1)+2000; // converts year

	printf("\nToday is the %d.%d.%d", day_pc, month_pc, year_pc); //outputs the current date on the screen
}

void matrix_display() //matrix display function
{
 FILE *fromfile;     //Variable pointer to a file
   fromfile = fopen ("graph_matrix.txt", "r"); //opens file for reading
   char content_in[60]; //Contains string value to write into the file

   printf("\nThe matrix stored in disk file looks like this:\n\n"); //output

   while (!feof(fromfile))
   {
		fgets (content_in, 60, fromfile);     //Reads up to a next new line
        printf ("\n%s", content_in); //displays content of text file
   }
   fclose(fromfile); //closes file
   printf("\n\n"); //new lines
}

void matrix_input() //matrix input function
{
  //variable declarations
   FILE *tofile;     //Variable pointer to a file
   char name_in[30]; //Contains string value to write into the file
   int two_d[50][50]; //two dimensional array storing the matrix
   int n = 0; //number of equations
   int n_store;	//stores the number of equations
   int i = 1; //counter
   int j = 0; //counter
   int save; //buffer variable
   int calc = 0; //calculates the sum of all numbers in a line
   int counter = 1; //counter
   int first = 1;	//first element of two_d array (lines)
   int second = 0;	//second element of two_d array	(rows)
   int q = 0; //counter
   int g = 1; //counter

   tofile = fopen ("graph_matrix.txt", "w"); //This opens the output file
   printf("\nPlease input the number of equations you want to process!(e.g.3) "); //prompts user for input
   scanf("%d", &n); //scans user input
   fprintf (tofile, "%d", n); //writing user input to the file
   n_store = n; //sets n_store to n
   printf("\nNow the numbers for row 1 should be inputted\n"); //output
 
	//first line of matrix is built
	while (i <= n_store)
	{
		printf("Please type %d.matrix field(e.g. 3): ", i); //prompts user for input
		scanf("%s", &name_in); //scans user input
		save = atoi(name_in);  //converts user input to integer
		two_d[0][second] = save; //saves user input in array
		i++;		//incrementing i
		second++;	//incrementing the row 
	}

	//resetting counters, lines and rows
	i = 0;
	first = 1;
	second = 0;

	for (i = 1; i < n; i++) //for-loop incrementing i
	{
		printf("\nThe next row starts now!\n"); //output
		for (j = g; j < n; j++) //for-loop incrementing j
		{
			printf("Please type next number(e.g.4): "); //prompts user for input
			scanf("%s", &name_in); //scans user input
			save = atoi(name_in);	//converts user input to integer
			two_d[i][j] = save;		//saves user input in array
		}
		g++; //incremting g
	}

	while (first <= n_store)
	{
		q = n_store; //setting q to n_store
		for (int f = first; f > 0; f--) //for-loop decrementing f
		{
			two_d[first][f-1] = two_d[f-1][first]; //setting the quadratic matrix (e.g. a12 = a21)
			second++; //incrementing row
		}
		    first++; //incrementing line
	}


	//output into text file
	for (int y = 0; y<=(n_store-1);y++) //for-loop incrementing y
	{
		calc = 0; //setting calc to 0
		fprintf (tofile, "\n");	//writing a new line to the file
		for (int z = 0; z<=(n_store-1); z++) //for-loop incrementing z
		{
			fprintf (tofile, "%d  ", two_d[y][z]); //Writing array to file
			calc = calc + two_d[y][z]; //calculating the sum of a line
		}
		fprintf(tofile, "%d", calc); //writing calc to the file
	}

    fclose(tofile); //close file

	n_store = q; //setting n_store to q again
	printf("\n\n\n"); //printing new lines

	//output on screen
	printf("Your matrix now looks like this:\n\n"); //output
	printf("%d\n", n); //output number of equations
	for (y = 0; y<=(n_store-1);y++) //for-loop incrementing y
	{
		calc = 0; //setting calc to 0
		for (int z = 0; z<=(n_store-1); z++) //for-loop incrementing z
		{
			printf("%d  ", two_d[y][z]); //output array to screen
			calc = calc + two_d[y][z];	//calculating the sum of a line
		}
		printf("%d", calc);		//output sum of a line
		printf("\n");	//new line
	}
	printf("\n"); //new line
}


void matrix_update() //dummy function
{
	printf("\nNot available");
}

void matrix_generate() //generates automatically a new matrix of linear equations
{
	
	int vertex, i, j;
	double **arry,*length, Lij;
	FILE *fp;
	fp = fopen("new_graph_matrix.txt", "w");   //call newstaff.txt file and mode is write mode
	printf("Input the number of linears ex 4) : ");	//print
	scanf("%d",&vertex);	//input number of linears
	printf("You input  %d \n",vertex);	//echo
	
	arry=(double**)malloc(vertex+2*sizeof(double*));//memory allocate
	
	for(i=0;i < vertex;i++)
		arry[i]=(double *)malloc(vertex+1*sizeof(double));//memory allocate
	
	length=(double *)malloc(vertex*sizeof(double));//memory allocate
	
	for(i=0;i<vertex-1;i++)
	{
		printf("Input length %d to %d ex 2) : ",i+1,i+2); //print
		scanf("%lf",&length[i]);		//input length
	}
	for(i=0;i<vertex;i++)
	{
		Lij=0;	// initialization
		for(j=0;j<=vertex;j++)
		{
			if(i>j)
				arry[i][j]=arry[j][i]; //must symmetrical
			
			else if(i==j)
			{
				arry[i][j]=1;			//aii must '1'
			}
			else
			{
				
				
				Lij=Lij+length[j-1];
				arry[i][j]=0.26*0.52/Lij; //calculate aij
			}
		}
	}
	arry[vertex-1][vertex]=0;
	for(i=0;i<vertex-1;i++)
	{
		printf("Input D%d ex 3): ",i+1);//print
		scanf("%lf",&arry[i][vertex]); //scanf number of linear
		arry[vertex-1][vertex]= arry[vertex-1][vertex]+arry[i][vertex];//calculate last B
	}
	
	arry[vertex-1][vertex]=arry[vertex-1][vertex]*(-1);  // last bi is balance
	
	
	for(i=0;i<vertex;i++)
	{ 
		for(j=0;j<=vertex;j++){
			printf("%lf",arry[i][j]); //print arry
			if(j!=vertex){
				printf("  ");	//print space
			}
			
		}
		if(i!=vertex-1){
			printf("\n");	//line change
		}
	}
	
	fprintf(fp, "%d\n",vertex);
	for(i=0;i<vertex;i++)
	{ 
		for(j=0;j<=vertex;j++){
			fprintf(fp, "%f",arry[i][j]);  //print to file
			if(j!=vertex){
				fprintf(fp,"  ");	//print space to file
			}
			
		}
		if(i!=vertex-1){
			fprintf(fp,"\n");	//line change in file
		}
	}
	fclose(fp);	//file close
}

void matrix_resolve()  //matrix resolve function (integer input)
{
	//variable declarations
	FILE *tofile;//pointer to file
	int amount=0;//amount of numbers in a row
	int a=0, b=0, c=0, d=0;//loop counters
	int i = 0;	//line counter in matrix
	int j = 0;	//row counter in matrix
	int content[50]={0};//stores the content of the file
	float matrix[10][10]={0};//matrix as float
	int matrix2[10][10];	 //matrix as int

	printf("\n"); //new line
    tofile=fopen("graph_matrix.txt","r"); //open file for reading
	fscanf(tofile,"%d",&amount); //getting the amount of numbers in a row
	printf("\nNumber of equations:  %d",amount); //output

	while (i<(amount*10))
	{
		fscanf(tofile,"%d",&content[i]); //scans the file and puts the content into the array content[]
		i++;//increment i
	}

	for (i=0;i<amount;i++)
	{
		for (j=0;j<(amount+1);j++)
		{
			matrix[i][j]=content[d];  //puts the content of the file into the two-dimensional matrix array
			d++; //increment p
		}
	}

	printf("\n\nThe matrix from the text file looks like this:\n"); //output
	printf("\n"); //new line

	for (i=0;i<amount;i++) //for-loop incrementing i (lines)
	{
		for (j=0;j<(amount+1);j++) //for-loop incrementing j (rows)
		{
			matrix2[i][j] = int (matrix[i][j]); //converting float matrix to int matrix
			printf("%d  ",matrix2[i][j]);  //displaying the int matrix on the screen
		}
		printf("\n"); //new line
	}

	printf("\n"); //new line

	//algorithm for solving matrix
	do
	{
		for (i=c;i<amount;i++) //for-loop incrementing i
		{
			for (j=amount;j>=0;j--) //for-loop decrementing j
			{
				if (matrix[i][c]!=0)//division by 0 not possible
				{
					matrix[i][j]=matrix[i][j]/matrix[i][c]; //divide matrix line through row
				}
			}
		}			
		a++; //incrementing a

		for (j=(amount);j>=0;j--) //for-loop decrementing j
		{
			for (i=a;i<(amount);i++) //for-loop incrementing i
			{
				if (matrix[i][c]!=0)//if number is 0
				{
					matrix[i][j]=matrix[i][j]-matrix[c][j]; //substract matrix line with next matrix line
				}
			}
		}
		c++;//next row
	}
	while(c<(amount-1)); //do as often as rows exist

	for (i=c;i<amount;i++) //for-loop incrementing i
	{
		for (j=amount;j>=0;j--)	//for-loop decrementing j
			{
				matrix[i][j]=matrix[i][j]/matrix[i][c]; //divide matrix line by next number
			}
	}

	b=2;

	for (j=(amount-1);j>0;j--) //for-loop decrementing j
	{
		for (i=(amount-b);i>=0;i--) //for-loop decremting i
		{
			matrix[i][j]=matrix[i][j]*matrix[j][amount]; //matrix line multiplied with last number of row
			matrix[i][amount]=matrix[i][amount]-matrix[i][j]; //last number of row equals the difference
		                 //between last number of row and matrix line
		}

		b++;
	}
		
	printf("\nThe results after solving the matrix are:\n\n");

	//output of results on the screen
	for (i=0;i<amount;i++) //for-loop incrementin i
	{
		printf("x%d = %f\n",i,matrix[i][amount]);
	}
	printf("\n"); //new line

	fclose(tofile); //close file


	tofile=fopen("graph_variables.txt","w");//open file for writing

	for (i=0;i<amount;i++) //for-loop incrementing i
	{
		fprintf(tofile,"%f\n",matrix[i][amount]); //writing results to file
	}

	fclose(tofile);//close file
}