#!/usr/bin/env python
import heapq
from sets import Set
import math

def Prim(G):
    a = [math.inf] * len(G[0])
    Q = [] # priority queue
    for v in range(len(G[0])):
        heapq.heappush(Q, v)
    S = Set([])  # set of explored nodes S <- phi

    while (Q[0] != None):  # Does this seem right?
        u = heapq.heappop(Q)
        S.union(u)
        for v in range(len(G[0])):
            if u == v:
                continue
            if v not in S and G[u][v] < a[v]:
                decrease priority a[v] to c_e