Marks obtained by a batch of students in
the Annual Examination are tabulated as follows:
Student name
Marks obtained
S.Laxmi
45 67 38
55
V.S.Rao
77 89 56 69
- -
- - - -
It is required
to compute the total marks obtained by each student and print the rank list
based on the total marks.
The program in
Fig.11.14 stores the student names in the array name and the marks in the array marks. After computing the
total marks obtained by all the students, the program prepares and prints the
rank list. The declaration
int marks[STUDENTS][SUBJECTS+1];
defines marks as a pointer to the array's first
row. We use rowptr as the pointer to the row of marks. The rowptr is initialized as follows:
int (*rowptr)[SUBJECTS+1] = array;
Note that array is the formal argument whose
values are replaced by the values of the actual argument marks. The parentheses
around *rowptr makes the rowptr as a pointer to an array of SUBJECTS+1 integers. Remember, the statement
int *rowptr[SUBJECTS+1];
would declare rowptr as an array of SUBJECTS+1
elements.
When we increment the rowptr (by rowptr+1),
the incrementing is done in units of the size of each row of array, making rowptr point to the next row.
Since rowptr points to a
particular row, (*rowptr)[x] points
to the xth element in the row.
POINTERS AND TWO-DIMENSIONAL ARRAYS
Program
#define STUDENTS
5
#define SUBJECTS
4
#include <string.h>
main()
{
char name[STUDENTS][20];
int marks[STUDENTS][SUBJECTS+1];
printf("Input
students names & their marks in four subjects\n");
get_list(name, marks, STUDENTS, SUBJECTS);
get_sum(marks, STUDENTS, SUBJECTS+1);
printf("\n");
print_list(name,marks,STUDENTS,SUBJECTS+1);
get_rank_list(name, marks, STUDENTS, SUBJECTS+1);
printf("\nRanked List\n\n");
print_list(name,marks,STUDENTS,SUBJECTS+1);
}
/* Input
student name and marks */
get_list(char *string[ ],
int array [ ] [SUBJECTS +1], int m,
int n)
{
int
i, j, (*rowptr)[SUBJECTS+1] = array;
for(i = 0; i < m;
i++)
{
scanf("%s",
string[i]);
for(j = 0; j < SUBJECTS; j++)
scanf("%d",
&(*(rowptr + i))[j]);
}
}
/*
Compute total marks obtained by each student */
get_sum(int array [ ] [SUBJECTS +1], int m,
int n)
{
int
i, j, (*rowptr)[SUBJECTS+1] = array;
for(i = 0; i < m;
i++)
{
(*(rowptr + i))[n-1] = 0;
for(j =0; j < n-1; j++)
(*(rowptr + i))[n-1] += (*(rowptr
+ i))[j];
}
}
/*
Prepare rank list based on total marks */
get_rank_list(char *string [ ],
int array [ ] [SUBJECTS +
1]
int m,
int n)
{
int i, j, k, (*rowptr)[SUBJECTS+1] =
array;
char *temp;
for(i = 1; i <= m-1; i++)
for(j = 1; j <= m-i; j++)
if( (*(rowptr + j-1))[n-1] <
(*(rowptr + j))[n-1])
{
swap_string(string[j-1],
string[j]);
for(k = 0; k < n; k++)
swap_int(&(*(rowptr +
j-1))[k],&(*(rowptr+j))[k]);
}
}
/* Print out the ranked list */
print_list(char *string[
],
int array [] [SUBJECTS + 1],
int m,
int n)
{
int
i, j, (*rowptr)[SUBJECTS+1] = array;
for(i = 0; i < m; i++)
{
printf("%-20s",
string[i]);
for(j = 0; j < n; j++)
printf("%5d", (*(rowptr
+ i))[j]);
printf("\n");
}
}
/* Exchange of integer values */
swap_int(int *p, int *q)
{
int
temp;
temp = *p;
*p
= *q;
*q
= temp;
}
/*
Exchange of strings
*/
swap_string(char s1[ ], char
s2[ ])
{
char
swaparea[256];
int
i;
for(i = 0; i < 256;
i++)
swaparea[i] = '\0';
i
= 0;
while(s1[i] != '\0' && i <
256)
{
swaparea[i] = s1[i];
i++;
}
i = 0;
while(s2[i] != '\0' && i <
256)
{
s1[i] = s2[i];
s1[++i] = '\0';
}
i = 0;
while(swaparea[i] != '\0')
{
s2[i] = swaparea[i];
s2[++i] = '\0';
}
}
Output
Input students names & their marks in
four subjects
S.Laxmi 45 67 38 55
V.S.Rao 77 89 56 69
A.Gupta 66 78 98 45
S.Mani 86 72 0 25
R.Daniel 44 55 66 77
S.Laxmi 45 67
38 55 205
V.S.Rao 77 89
56 69 291
A.Gupta 66 78
98 45 287
S.Mani 86 72
0 25 183
R.Daniel 44 55
66 77 242
Ranked List
V.S.Rao 77 89
56 69 291
A.Gupta 66 78
98 45 287
R.Daniel 44 55
66 77 242
S.Laxmi 45 67
38 55 205
S.Mani 86 72
0 25 183
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