Gale Shapley algorithm for stable matching.
Input: Object of class Map<String,List<String>>, in which each key is a node name, and its value is an ordered list of names denoting preferences (the first element being the highest preference). The input contains 2n elements, n of which are “male” and include each of the n “female” nodes in their preference list, and vice versa. The order of the elements in the input map does not matter, and "male" vs. "female" elements will be determined based on the composition of the preference lists (a "male" element will have only "female" elements in their preference list while a "female" element will have only "male" elements in their preference list").
Output: Object of class Map<String,String> where each key is paired with its value.
Suitor Bias: The Gale-Shapley algorithm is biased for 'suitor optimality'. The suitor in this implementation will be the "gender" (group) opposite that of the first element. For more information on the Gale-Shapley algorithm see: http://en.wikipedia.org/wiki/Stable_marriage_problem.
Sample: In the Sample Input and Sample Output below, "Andre" and "Ritesh" are male while "Shikha" and "Joanne" are female. The 'suitor' in this case will be the females, as the first element "Andre" is male.