When I print the string returned by each of your put_bracket calls, the output does not match the required output for 3 and 4: 
CCC[ATCTG]TCCTT[ATTTG]CTG
AC[CCATC]TGTCCTTGGCCAT
[CCACC]A[GCACC]TGTC
C[CCAAC]ACCTGCTGCCT

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In reply to Re: Answer: How do I put bracket on substring(s) of a string? by toolic
in thread How do I put bracket on substring(s) of a string? by monkfan

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