Added code for B/W balls #32:

[anushka-220]

Fixes #32

Input Taken:
This code reads a binary string s where each character is either '0' (white ball) or '1' (black ball).

Logic used:
It iterates through the length of the string once using a for loop.
The variable 'swaps' stores the minimum required swaps to get black balls on the right and white balls on the left.
Using a variable 'white_balls' , we have kept a track of the number of balls encountered so far.
For each white ball ('0'), the program adds the current count of 'white_balls' to the 'swaps' variable.
For each black ball ('1'), it increments the white_balls counter.

Output:
The program calculates and outputs the minimum number of swaps needed to rearrange the balls.

[Saket6198]

@anushka-220
in your cpp file itself, write the working of your code/ algorithm