Lexicographically Smallest String Construction | Dataford Interview Questions

Given S1 and a T/F string S2, generate the lexicographically smallest string of length L1+L2-1 where S1 appears at index i iff S2[i] is T, else -1.

Asked in the OA stage. Return "-1" if the constraints are inconsistent. The output must contain lowercase English letters.

Input and Output

Implement build_string(s1, s2). s1 is the required substring and s2 contains one character per possible starting index. Return the lexicographically smallest valid string, or "-1" when none exists.

Constraints

1 <= len(s1), len(s2) <= 2000
s2 contains only 'T' and 'F'
The output contains lowercase English letters or equals "-1"

Function Signature

def build_string(s1, s2):

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