Notes

#include <stdio.h>
#include <string.h>
#define size 10
int isNeg = 1;
void pt(int *base,int order)
{
int i, j;
for(i=0;i<order;i++)
{
for(j=0;j<order;j++)
printf("%dt", *(base+(i*size)+j));
printf("n");
}printf("DONEn");
}

int gcd(int m, int n)
{
if(n==0)
return m;
else
return gcd(n,m%n);
}


void changeRow(int *base,int row, int pivotRow, int pivotLoc, int order)
{
/*

row = the row to be reduced
pivotRow = WRT which row
pivotLoc = Start from this location, mostly equal to pivot row
order = nxn
*/

//mat[i][j] = *(*(base+i)+j)
int j;

int num2 = *(base+(row*size)+pivotLoc);
int pivot = *(base+(pivotRow*size)+pivotLoc);
if(num2 == 0) return;
int gc = gcd(num2,pivot);
num2 = num2/gc;
pivot = pivot/gc;
//printf("npivot %d %dn",pivot,num2);
for(j=pivotLoc;j<order;j++)
{
//printf("Chamging %d to %d-%dn",*(base+(row*size)+j), *(base+(row*size)+j) * pivot ,(*(base+(pivotRow*size)+j))* num2);
*(base+(row*size)+j) = *(base+(row*size)+j) * pivot - (*(base+(pivotRow*size)+j))* num2;
}
pt(base,order);
}


void swapRow(int *base, int row1, int order)
{
int j;
for(j=row1;j<order;j++)
if(*(base+(j*size)+row1) != 0)
break;
int row2 = j;
if(row2>=order) return;

for(j=0;j<order;j++)
{
int tmp = *(base+(row1*size)+j);
*(base+(row1*size)+j) = *(base+(row2*size)+j);
*(base+(row2*size)+j) = tmp;
}
isNeg = -isNeg;
printf("swapped R%d to R%dn", row1, row2);
pt(base,order);
}

int main(){
//************************************************************
//Getting inut and checking if square and showing the matrix
char input[256];
fgets(input,256,stdin); //take input row wise as string separated by space
int i,j,k,row,col,negFlag = 1;
row = 0; col = 0;
int mat[size][size], rowsize[size];

do{
int no = 0;
for(i=0;(k=input[i])!=10;i++)
{

if(k == 45) // if - means negative number
negFlag = -1;
else if(k!=32)//Not Space
no = (10*no) + k -'0';
else //if sace then save the number as element of array
{
mat[row][col++] = negFlag * no;
negFlag = 1;
no=0;
}
}
mat[row][col++] = negFlag * no; // last number as there is no space at the end
rowsize[row] = col; //save no of elements for square matrix comparision
row++; col = 0; no=0; // reset the values
fgets(input,256,stdin); // Next row input
}while(input[0]!='$'); //$ is the end signal

for(i=0;i<row;i++)
if(rowsize[i] != row)
{printf("NOT SQUAREn"); return 0;}
printf("SQUARE and The Matrix isn");
int order = row;
pt(&mat[0][0],order);
//*********************************************************

// Determinant
int det = 1;
int bias = 1;
for(i=0;i<order;i++)
{
det = det*mat[i][i];
if(mat[i][i] == 0)
printf("%d is zeron",mat[i][i]),swapRow(&mat[0][0],i,order);
for(j=i+1;j<order;j++)
changeRow(&mat[0][0],j,i,i,order),bias = bias*gcd(mat[i][i],mat[j][i]);
}

printf("%dn", bias);

printf("DET = %dn", isNeg*det/bias);

}