Given a string of red and blue balls, find min number of swaps to club the colors together
- by efficiencyIsBliss
We are given a string of the form: RBBR, where R - red and B - blue. 
We need to find the minimum number of swaps required in order to club the colors together. In the above case that answer would be 1 to get RRBB or BBRR. 
I feel like an algorithm to sort a partially sorted array would be useful here since a simple sort would give us the number of swaps, but we want the minimum number of swaps. 
Any ideas? 
This is allegedly a Microsoft interview question according to this.