Given two strings s1 and s2(call letters in uppercase). Check if it is possible to convert s1 to s2 by performing following operations.
1. Make some lowercase letters uppercase.
2. Delete all the lowercase letters.
Input : s1 = daBcd s2 = ABC Output : yes Explanation : daBcd -> dABCd -> ABC Covert a and b at index 1 and 3 to upper case, delete the rest those are lowercase. We get the string s2. Input : s1 = argaju s2 = RAJ Output : yes Explanation : argaju -> aRgAJu -> RAJ convert index 1, 3 and 4 to uppercase and then delete. All lowercase letters Input : s1 = ABcd s2= BCD Output : NO
Let DPi, j be 1 if it is possible to convert 1st i characters of s1 to j characters of s2, else DPi, j=0. Close observations gives us two conditions to deal with.
Initially DP0, 0=1, if DPi, j=1 then it is possible to check for next sets using following conditions.
1. If s1[i] in upper case is equal to s2[j] then it is possible to convert i+1 characters of s1 to j+1 characters of s2, hence DPi+1, j+1=1.
2. If s1[i] is in lower case, then it is possible to delete that element and hence i+1 characters can be converted to j characters of s2. Hence DPi+1, j=1.
If DPn, m=1, then it is possible to convert s1 to s2 by following conditions.
Below is the CPP illustration of the above approach.