doubt

Question

How many total numbers of substrings are possible out of the string abbbccd ?

can i apply  [n(n+1)/2 +1 ] here ?

Answer 1

even formula of substring is (n(n+1)/2)+1

but here due to repeatition it will be 25...

explaination-

sub-String of length 0 {epsilon}
sub-String of length 1 {a,b,c,d}
sub-String of length 2 {ab,bb,bc,cc,cd}
sub-String of length 3 {abb,bbb,bbc,bcc,ccd}
sub-String of length 4 {abbb,bbbc,bbcc,bccd}
sub-String of length 5 {abbbc,bbbcc,bbccd}
sub-String of length 6 {abbbcc,bbbccd}
sub-String of length 7 {abbbccd}
Total= 1+4+5+5+4+3+2+1= 25