freeCodeCamp/curriculum/challenges/chinese/07-scientific-computing-with-python/learn-algorithm-design-by-building-a-shortest-path-algorithm/657891ab9c1903f4e55433ba.md

id, title, challengeType, dashedName

id	title	challengeType	dashedName
657891ab9c1903f4e55433ba	Step 44	20	step-44

--description--

When the condition of your new if is true, a shorter path to the neighbor node has been found.

Inside your new if block, delete pass and reassign the neighbor node distance to the sum of the neighbor node distance plus the distance of current.

--hints--

You should assign distance + distances[current] to distances[node] inside your new if.

({ test: () =>  {
    const commentless_code = __helpers.python.removeComments(code);
    const {block_body} = __helpers.python.getBlock(commentless_code, /if\s+distance\s*\+\s*distances\s*\[\s*current\s*\]\s*<\s*distances\s*\[\s*node\s*\]\s*/);
    assert(block_body.match(/^\s+distances\s*\[\s*node\s*\]\s*=\s*distance\s*\+\s*distances\s*\[\s*current\s*\]/));
  }
})

--seed--

--seed-contents--

my_graph = {
    'A': [('B', 3), ('D', 1)],
    'B': [('A', 3), ('C', 4)],
    'C': [('B', 4), ('D', 7)],
    'D': [('A', 1), ('C', 7)]
}

def shortest_path(graph, start):
    unvisited = list(graph)
    distances = {node: 0 if node == start else float('inf') for node in graph}
    paths = {node: [] for node in graph}
    paths[start].append(start)

    while unvisited:
        current = min(unvisited, key=distances.get)
        for node, distance in graph[current]:
--fcc-editable-region--
            if distance + distances[current] < distances[node]:
                pass
--fcc-editable-region--
    print(f'Unvisited: {unvisited}\nDistances: {distances}\nPaths: {paths}')

#shortest_path(my_graph, 'A')