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Chain a list of tuples.
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| # We can sort using a custom adjacency index that allows us to pick the starting node. | |
| tickets = [('PHL','NYC'),('IAD','PHL'),('SFO','IAD'),('NYC','SFO')] | |
| sortedTickets = [] | |
| index = {} | |
| for t in tickets: | |
| if t[0] not in index: | |
| index[t[0]] = t | |
| def getNext(ticket): | |
| return index[ticket[1]] | |
| currentTicket = tickets[0] | |
| while len(tickets): | |
| sortedTickets.append(currentTicket) | |
| tickets.remove(currentTicket) | |
| currentTicket= getNext(currentTicket) | |
| print sortedTickets | |
| #[('PHL', 'NYC'), ('NYC', 'SFO'), ('SFO', 'IAD'), ('IAD', 'PHL')] |
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| # We can sort using a custom adjacency index that allows us to pick the starting node. | |
| tickets = [('PHL','NYC'),('IAD','PHL'),('SFO','IAD'),('NYC','SFO')] | |
| sortedTickets = [] | |
| index = {} | |
| for t in tickets: | |
| if t[0] not in index: | |
| index[t[0]] = {} | |
| index[t[0]]['src'] = t | |
| if t[1] not in index: | |
| index[t[1]] = {} | |
| index[t[1]]['dest'] = t | |
| def getNext(ticket): | |
| return index[ticket[1]]['src'] | |
| def getPrev(ticket): | |
| return index[ticket[0]]['dest'] | |
| currentTicket = tickets[0] | |
| while len(tickets): | |
| sortedTickets.append(currentTicket) | |
| tickets.remove(currentTicket) | |
| currentTicket= getNext(currentTicket) | |
| print sortedTickets | |
| #[('PHL', 'NYC'), ('NYC', 'SFO'), ('SFO', 'IAD'), ('IAD', 'PHL')] |
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| # We can sort using a comparison function but we have no control over starting node. | |
| tickets = [('PHL','NYC'),('IAD','PHL'),('SFO','IAD'),('NYC','SFO')] | |
| def compareTix(a,b): | |
| if a[0] == b[1]: | |
| return 1 | |
| if a[1] == b[0]: | |
| return -1 | |
| return 0 | |
| tickets.sort(cmp=compareTix) | |
| print tickets | |
| #[('NYC', 'SFO'), ('SFO', 'IAD'), ('IAD', 'PHL'), ('PHL', 'NYC')] |
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| import networkx as nx | |
| # Using a graph we can find the cycle for a given start node. | |
| G=nx.Graph([('PHL','NYC'),('IAD','PHL'),('SFO','IAD'),('NYC','SFO')]) | |
| print list(nx.cycle_basis(G,'PHL')) | |
| # [['NYC', 'SFO', 'IAD', 'PHL']] | |
| # Using a directed graph we can find the cycles, but can't pick the start node. | |
| DG=nx.DiGraph([('PHL','NYC'),('IAD','PHL'),('SFO','IAD'),('NYC','SFO')]) | |
| print list(nx.simple_cycles(DG)) | |
| # [['NYC', 'SFO', 'IAD', 'PHL']] |
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