CF223B Two Strings

A subsequence of length $ |x| $ of string $ s=s_{1}s_{2}...\ s_{|s|} $ (where $ |s| $ is the length of string $ s $ ) is a string $ x=s_{k1}s_{k2}...\ s_{k|x|} $ $ (1

N/A

N/A

In the first sample string $ t $ can occur in the string $ s $ as a subsequence in three ways: abab, abab and abab. In these occurrences each character of string $ s $ occurs at least once. In the second sample the 4-th character of the string $ s $ doesn't occur in any occurrence of string $ t $ . In the third sample there is no occurrence of string $ t $ in string $ s $ .