java - 递归方法打印太多次？

标签 java recursion arraylist output

所以我有一个方法，可以递归地对 GeometricObjects 的数组列表进行排序，并按其区域的顺序将它们打印出来。但是，我似乎无法弄清楚这个小问题。我的方法正确地打印出数据，但它打印了 arraylist 6 次而不是一次(它包含 6 个对象)，知道我做错了什么吗？谢谢!

private static void recursionSort(ArrayList<GeometricObject> list, int low, int high){
    if (low < high){
        int minIndex = low;
        GeometricObject min = list.get(low); //set min to first object in range
        for (int i = low + 1; i <= high; i++){ //loop through all values other than first
            if (list.get(i).getArea() < min.getArea()){ //check if the value is smaller than current min
                min = list.get(i); //if it is update the min
                minIndex = i; //store min index so we can swap locations later
            }
        }

        Collections.swap(list, low, minIndex); //move the original min to new min's old index (tricky wording)
        list.set(low, min); //set the old lowest to the new lowest using store min value

        recursionSort(list, low + 1, high); //call it again

    }
    System.out.println("Recursion sort:" + list);

}

期望的输出:

Recursion sort:[GeometricObject [color=blue, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=2.0  Area=12.57  Perimeter=12.57 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=4.0  Area=50.27  Perimeter=25.13 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=5.0 Width= 11.0  Area=55.0  Perimeter=32.0 ]
, GeometricObject [color=orange, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=10.0 Width= 6.0  Area=60.0  Perimeter=32.0 ]
, GeometricObject [color=red, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=14.0 Width= 12.0  Area=168.0  Perimeter=52.0 ]
, GeometricObject [color=blue, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=15.0  Area=706.86  Perimeter=94.25 ]
]

我收到的输出

Recursion sort:[GeometricObject [color=blue, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=2.0  Area=12.57  Perimeter=12.57 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=4.0  Area=50.27  Perimeter=25.13 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=5.0 Width= 11.0  Area=55.0  Perimeter=32.0 ]
, GeometricObject [color=orange, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=10.0 Width= 6.0  Area=60.0  Perimeter=32.0 ]
, GeometricObject [color=red, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=14.0 Width= 12.0  Area=168.0  Perimeter=52.0 ]
, GeometricObject [color=blue, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=15.0  Area=706.86  Perimeter=94.25 ]
]
Recursion sort:[GeometricObject [color=blue, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=2.0  Area=12.57  Perimeter=12.57 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=4.0  Area=50.27  Perimeter=25.13 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=5.0 Width= 11.0  Area=55.0  Perimeter=32.0 ]
, GeometricObject [color=orange, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=10.0 Width= 6.0  Area=60.0  Perimeter=32.0 ]
, GeometricObject [color=red, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=14.0 Width= 12.0  Area=168.0  Perimeter=52.0 ]
, GeometricObject [color=blue, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=15.0  Area=706.86  Perimeter=94.25 ]
]
Recursion sort:[GeometricObject [color=blue, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=2.0  Area=12.57  Perimeter=12.57 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=4.0  Area=50.27  Perimeter=25.13 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=5.0 Width= 11.0  Area=55.0  Perimeter=32.0 ]
, GeometricObject [color=orange, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=10.0 Width= 6.0  Area=60.0  Perimeter=32.0 ]
, GeometricObject [color=red, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=14.0 Width= 12.0  Area=168.0  Perimeter=52.0 ]
, GeometricObject [color=blue, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=15.0  Area=706.86  Perimeter=94.25 ]
]
Recursion sort:[GeometricObject [color=blue, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=2.0  Area=12.57  Perimeter=12.57 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=4.0  Area=50.27  Perimeter=25.13 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=5.0 Width= 11.0  Area=55.0  Perimeter=32.0 ]
, GeometricObject [color=orange, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=10.0 Width= 6.0  Area=60.0  Perimeter=32.0 ]
, GeometricObject [color=red, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=14.0 Width= 12.0  Area=168.0  Perimeter=52.0 ]
, GeometricObject [color=blue, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=15.0  Area=706.86  Perimeter=94.25 ]
]
Recursion sort:[GeometricObject [color=blue, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=2.0  Area=12.57  Perimeter=12.57 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=4.0  Area=50.27  Perimeter=25.13 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=5.0 Width= 11.0  Area=55.0  Perimeter=32.0 ]
, GeometricObject [color=orange, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=10.0 Width= 6.0  Area=60.0  Perimeter=32.0 ]
, GeometricObject [color=red, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=14.0 Width= 12.0  Area=168.0  Perimeter=52.0 ]
, GeometricObject [color=blue, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=15.0  Area=706.86  Perimeter=94.25 ]
]
Recursion sort:[GeometricObject [color=blue, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=2.0  Area=12.57  Perimeter=12.57 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=4.0  Area=50.27  Perimeter=25.13 ]
, GeometricObject [color=green, filled=false, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=5.0 Width= 11.0  Area=55.0  Perimeter=32.0 ]
, GeometricObject [color=orange, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=10.0 Width= 6.0  Area=60.0  Perimeter=32.0 ]
, GeometricObject [color=red, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Rectangle [ Height=14.0 Width= 12.0  Area=168.0  Perimeter=52.0 ]
, GeometricObject [color=blue, filled=true, dateOfCreation=Wed Oct 14 12:02:33 EDT 2015]
 Circle [ radius=15.0  Area=706.86  Perimeter=94.25 ]
]

最佳答案

这里的问题是每一级递归都会在返回之前打印出列表。

要解决此问题，您可以重载打印方法:

private static void recursionSort(ArrayList<GeometricObject> list){
    recursionSort(list, 0, list.size())
    System.out.println("Recursion sort:" + list);        
}

private static void recursionSort(ArrayList<GeometricObject> list, int low, int high){
    if (low < high){
        int minIndex = low;
        GeometricObject min = list.get(low); //set min to first object in range
        for (int i = low + 1; i <= high; i++){ //loop through all values other than first
            if (list.get(i).getArea() < min.getArea()){ //check if the value is smaller than current min
                min = list.get(i); //if it is update the min
                minIndex = i; //store min index so we can swap locations later
            }
        }

        Collections.swap(list, low, minIndex); //move the original min to new min's old index (tricky wording)
        list.set(low, min); //set the old lowest to the new lowest using store min value

        recursionSort(list, low + 1, high); //call it again

    }

}

关于java - 递归方法打印太多次？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/33132407/

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