Function sp_phragmen::build_support_map

pub fn build_support_map<AccountId>(
    winners: &[AccountId], 
    assignments: &[StakedAssignment<AccountId>]
) -> (SupportMap<AccountId>, u32) where
    AccountId: Default + Ord + Clone, 

Build the support map from the given phragmen result. It maps a flat structure like

assignments: vec![
	voter1, vec![(candidate1, w11), (candidate2, w12)],
	voter2, vec![(candidate1, w21), (candidate2, w22)]
]

into a mapping of candidates and their respective support:

 SupportMap {
	candidate1: Support {
		own:0,
		total: w11 + w21,
		others: vec![(candidate1, w11), (candidate2, w21)]
	},
	candidate2: Support {
		own:0,
		total: w12 + w22,
		others: vec![(candidate1, w12), (candidate2, w22)]
	},
}

The second returned flag indicates the number of edges who didn't corresponded to an actual winner from the given winner set. A value in this place larger than 0 indicates a potentially faulty assignment.

O(E) where E is the total number of edges.