Prim算法最小生成树-Python

qwurey的文章写的很好懂了，但是自己代码再写出来确实不一样，主要还是练一下基本功，自己基本功还不够，代码勉强凑合吧，可能过多一阵自己回来再看就能写出更好的。作者的图很好看，用什么画的呢。

VISITED = 999999  # 表示已经加入MST
DISCONNECT = 10000  # 表示无通路


def Prim(graph: dict, start: str) -> list:
    lowcost = [DISCONNECT]*len(graph)
    lowcost[int(start)-1] = VISITED
    mst = [start]*len(graph)  # 记录顶点的历史更新，用于回溯
    mst[int(start)-1] = 0
    visted = []
    visted.append(start)
    vist = [] # 用于输出
    node = start
    # 更新lowcost和mst
    while any(mst):
            lowcost, mst = update(graph[node], node, lowcost, mst)
            if node == mst[lowcost.index(min(lowcost))]:
                vist.append(node + '->' + str(lowcost.index(min(lowcost))+1))
                node, mst[lowcost.index(min(lowcost))] = str(lowcost.index(min(lowcost)) + 1), 0  # 找出到开始的顶点权值最小的顶点
            else:
                vist.append(str(mst[lowcost.index(min(lowcost))]) + '->' + str(lowcost.index(min(lowcost))+1))
                node, mst[lowcost.index(min(lowcost))] = str(lowcost.index(min(lowcost))+1), 0
            lowcost[lowcost.index(min(lowcost))] = VISITED
            visted.append(node)
    return vist


def update(edge: list, thisNode: str, lowcost: list, mst: list):
    for i in edge:
        if lowcost[int(i[0]) - 1] != VISITED and i[1] < lowcost[int(i[0]) - 1]:
            lowcost[int(i[0]) - 1] = i[1]
            mst[int(i[0])-1] = thisNode
    return lowcost, mst


if __name__ == "__main__":
    G = {
     '1': [['2', 6], ['3', 1], ['4', 5]],
         '2': [['1', 6], ['3', 5], ['5', 3]],
         '3': [['1', 1], ['2', 5], ['4', 5], ['5', 6], ['6', 4]],
         '4': [['1', 5], ['3', 5], ['6', 2]],
         '5': [['2', 3], ['3', 6], ['6', 6]],
         '6': [['3', 4], ['4', 2], ['5', 6]]}
    v = Prim(G, '1')
    for i in v:
        print(i)

Connected to pydev debugger (build 191.7141.48)
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