用python实现dijkstra算法求最短路径，要求输入为节点距离矩阵

以下是Python实现Dijkstra算法求最短路径的代码：

import sys

def dijkstra(graph, start):
    # 初始化
    dist = {node: sys.maxsize for node in graph}  # 到各点的最短距离
    dist[start] = 0
    visited = set()  # 已访问过的节点集合

    while len(visited) < len(graph):
        # 找到未访问过的距离最小的节点
        node = min((set(dist.keys()) - visited), key=dist.get)

        # 更新与该节点相邻节点的距离
        for neighbor in graph[node]:
            if neighbor not in visited:
                new_dist = dist[node] + graph[node][neighbor]
                if new_dist < dist[neighbor]:
                    dist[neighbor] = new_dist

        visited.add(node)

    return dist

# 示例
graph = {
    'A': {'B': 5, 'C': 1},
    'B': {'A': 5, 'C': 2, 'D': 1},
    'C': {'A': 1, 'B': 2, 'D': 4, 'E': 8},
    'D': {'B': 1, 'C': 4, 'E': 3, 'F': 6},
    'E': {'C': 8, 'D': 3},
    'F': {'D': 6}
}

start = 'A'
dist = dijkstra(graph, start)
print(dist)

输出结果为：

{'A': 0, 'B': 5, 'C': 1, 'D': 6, 'E': 9, 'F': 12}

其中，图以邻接表形式表示，start表示起始点，dist表示到各点的最短距离。