Given four integers l, m, x and y. The task is to check whether it is possible to make a binary string consisting of l 0’s, m 1’s, x “01” and y “10” as sub-sequences in it.
Input: l = 3, m = 2, x = 4, y = 2
Possible string is “00110”. It contains 3 0’s, 2 1’s,
4 “01” sub-sequences and 2 “10” sub-sequences.
Input: l = 3, m = 2, x = 4, y = 3
No such binary string exists.
Approach: The possible string is always of the form 00…11…00…. First consists of some number of zeroes, then all ones and then the remaining number of zeros.
Let l1 be the number of zeros before ones and l2 be the number of zeros after ones then the equations are:
- l1 + l2 = l (Total number of zeros).
- l1 * m = x (Number of “01” sub-sequences).
- m * l2 = y (Number of “10” sub-sequences).
From the above three equations, we get x + y = l * m. If this equation fails for the given values then the string is not possible else print Yes.
Below is the implementation of the above approach:
Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.