freeCodeCamp/curriculum/challenges/chinese/07-scientific-computing-with-python/learn-algorithm-design-by-building-a-shortest-path-algorithm/6559d86fe1b8947954b9178d.md

id, title, challengeType, dashedName

id	title	challengeType	dashedName
6559d86fe1b8947954b9178d	Step 56	20	step-56

--description--

Now it's better but you don't want to print the details about the starting node.

Before the print call, add an if statement to execute when node is equal to start and use the continue keyword to go to the next loop iteration.

--hints--

你应该在 for 循环中嵌套一个 if 语句，以检查 node 是否等于 start 。

({ test: () =>  {
    const shortest = __helpers.python.getDef(code, "shortest_path");
    const {function_body} = shortest;    
    assert(function_body.match(/^(\s{4})for\s+node\s+in\s+targets_to_print\s*:\s*^\1\1if\s+(node\s*==\s*start|start\s*==\s*node)\s*:/m));
  }
})

You should use the continue keyword to go to the next iteration inside your new if statement.

({ test: () =>  {
    const shortest = __helpers.python.getDef(code, "shortest_path");
    const {function_body} = shortest;    
    assert(function_body.match(/^(\s{4})for\s+node\s+in\s+targets_to_print\s*:\s*^\1\1if\s+(node\s*==\s*start|start\s*==\s*node)\s*:\s*^\1\1\1continue/m));

  }
})

--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, target = ''):
    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]:
            if distance + distances[current] < distances[node]:
                distances[node] = distance + distances[current]
                if paths[node] and paths[node][-1] == node:
                    paths[node] = paths[current][:]
                else:
                    paths[node].extend(paths[current])
                paths[node].append(node)
        unvisited.remove(current)
--fcc-editable-region--  
    targets_to_print = [target] if target else graph
    for node in targets_to_print:
        print(f'\n{start}-{node} distance: {distances[node]}\nPath: {" -> ".join(paths[node])}')

shortest_path(my_graph, 'A')
--fcc-editable-region--