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  !------------------------------------------------------------------------
! The fortran subroutine CSRorCSC(R,C,V, n, nz) which converts
! the CSR representation of a sparse matrix to its CSC representation
!-------------------------------------------------------------------------
! Also a program which enters a sparse matrix (in the COO format) and 
! creates its CSR Representation, invokes the CSRorCSC Subroutine and 
! output the result.
!-------------------------------------------------------------------------

PROGRAM A7Q1
    
    IMPLICIT NONE
    ! DECLARE VARIABLES
    INTEGER, DIMENSION(:,:), ALLOCATABLE :: A
    INTEGER, DIMENSION(3) :: B
    INTEGER :: i, j, size, m, n, check, k, rowIndex
    ! R, C, V
    INTEGER, DIMENSION(:), ALLOCATABLE :: DUMMY
    INTEGER, DIMENSION(:), ALLOCATABLE :: R
    INTEGER, DIMENSION(:), ALLOCATABLE :: C
    INTEGER, DIMENSION(:), ALLOCATABLE :: V
    

    
    ! GET THE SPARSE MATRIX IN COO FORMAT
    DO 
        PRINT *, "ENTER THE (SIZE OF MATRIX) m and n (OR 0 0 to END): "
        READ *, m ,n

        IF (m .eq. 0 .or. n .eq. 0) STOP
        IF (m .lt. 0 .or. n .lt. 0) THEN
            PRINT *, "NEGATIVE NUMBER OF ELEMENTS: "
            
        ELSE
            ! ALLOCATE THE ARRAY A
            ALLOCATE(A(m,n))
            PRINT "(1X, 'ENTER THE MATRIX VALUES OF A', I3, '*', I3, ' ELEMENTS:')", m, n
            READ *, ((A(i, j), i = 1, m), j = 1, n)


            ! DISPLAY USER INPUT (LATER WE WILL USE THE FORMATTING.)
            PRINT *, "COO FORMAT : "
            DO i = 1,m
                PRINT "(5X,15I5)", A(i,1:n)
            END DO



            
            ! CSRorCSC FORMAT
            size = 1
            DO i = 1, m
                DO j = i, n
                    IF (A(i, j) /= 0) THEN
                        size = size + 1
                    END IF
                END DO
            END DO

            PRINT *, size   ! 8 for demo sparse matrix

            ! ALLOCATING R, C, V
            ALLOCATE(DUMMY(size), STAT = check)
            ALLOCATE(R(m), STAT = check)
            ALLOCATE(C(size), STAT = check)
            ALLOCATE(V(size), STAT = check)

            ! GETTING THE R,C,V FOR CSR
            k = 1
            rowIndex = 0
            DO i = 1, m
                DO j = 1, n
                    IF (A(i, j) /= 0) THEN
                        DUMMY(k) = i
                        rowIndex = rowIndex + 1
                        C(k) = j
                        V(k) = A(i, j)
                        k = k + 1
                    END IF
                END DO
                R(i) = rowIndex
            END DO


            PRINT *, "CSR FORMAT: "
            PRINT *, "R: ", DUMMY
            PRINT *, "R: ", R
            PRINT *, "C: ", C
            PRINT *, "V: ", V



        END IF
    END DO


END PROGRAM A7Q1