In c language how to remove duplicate consecutive row in csv file.

For example,

input:

3,4,4,4

3,4,4,4

3,5,4,4

3,4,4,4

output:

3,4,4,4

3,5,4,4

3,4,4,4

not remove all the duplicate but removeconsecutive duplicates.

and how to sort the csv file by its heading.

for example,

sorted by:c

input:

a,b,c

1,2,3

1,3,2

3,4,5

output:

a,b,c

1,3,2

1,2,3

3,4,5