Question

我正在尝试实现BFS算法以查找图中的所有路径（来自src和dest）。我使用切片来模拟队列，但是当我在for循环中向其附加多个元素时，该切片损坏（附加未按预期工作）。我不知道为什么。我是GoLand的新人

// GetPathsFromCache retrieve information from loaded jsons in the cache
func (cache *ModelsDataCache) GetPathsFromCache(modelUrn, selectedElement, targetType, authToken string, modelJSONs *ModelJSONs) []systemdetection.GraphPath {

    result := make([]systemdetection.GraphPath, 0)

    //create the queue which stores the paths
    q := make([]Path, 0)

    //Path to store the current path
    var currentPath Path
    currentPath.path = append(currentPath.path, selectedElement)
    q = append(q, currentPath)


    for len(q) > 0 {


        currentPath = q[0] //get top
        q = q[1:]


        lastInThePath := currentPath.path[len(currentPath.path)-1]
        connectedToTheCurrent := cache.GetConnectionsFromCache(modelUrn, lastInThePath, authToken, modelJSONs)

        lastInPathType := modelJSONs.Elements[lastInThePath].Type

        if lastInPathType == targetType {
            //cache.savePath(currentPath, &result)

            var newPath systemdetection.GraphPath
            newPath.Target = lastInThePath
            newPath.Path = currentPath.path[:]
            newPath.Distance = 666
            result = append(result, newPath)
        }


        for _, connected := range connectedToTheCurrent {
            if cache.isNotVisited(connected, currentPath.path) {


                var newPathN Path

                newPathN.path = currentPath.path
                newPathN.path = append(newPathN.path, connected)

                q = append(q, newPathN)
            }
        }

    }

    return result

}

Answer 1

您可能没有正确使用make。切片的make接受两个参数，长度和（可选）容量：

make([]T, len, cap)

Len是它包含的元素的起始数量，容量是它可以不扩展而可以包含的元素数量。有关A Tour of Go的更多信息。

视觉上：

make([]string, 5) #=> ["", "", "", "", ""]
make([]string, 0, 5) #=> [] (but the underlying array can hold 5 elements)

append添加到数组的末尾，因此遵循相同的示例：

arr1 := make([]string, 5) #=> ["", "", "", "", ""]
arr1 = append(arr1, "foo") #=> ["", "", "", "", "", "foo"] 

arr2 := make([]string, 0, 5) #=> []
arr2 = append(arr2, "foo") #=> ["foo"] (underlying array can hold 4 more elements before expanding)

您正在创建一定长度的切片，然后追加到末尾，这意味着切片的前N个元素为零值。将您的make([]T, N)更改为make([]T, 0, N)。

以下是前往“游乐场”的链接，其中显示了区别：https://play.golang.org/p/ezoUGPHqSRj

奇怪的切片行为

1 个答案: