Question

我正在创建快速排序以对距离特定城市最近的其他城市进行排序。

这是我的代码：

    private static void QuickSort(ArrayList<City> array, int First, int Last, City city ){
    int Low,High,MidDistance;
    Low = First;
    High = Last;
    Edge compareEdge = new Edge(array.get((First + Last)/ 2), city);
    MidDistance = compareEdge.computeDistance();

    do {
        compareEdge = new Edge(array.get(Low),city);
        while (compareEdge.computeDistance() < MidDistance){
            Low += 1;
            compareEdge = new Edge(array.get(Low),city);
        }

        compareEdge = new Edge(array.get(High),city);
        while (compareEdge.computeDistance() > MidDistance){
            High -= 1;
            compareEdge = new Edge(array.get(High),city);
        }

        if (Low <= High) {
                Swap(array,Low,High);
                Low = Low + 1;
                High = High - 1;
        }

    } while (Low <= High);

    if (First < High){
        QuickSort(array, First, High, city);
    }

    if (Low < Last){
        QuickSort(array, Low, Last, city);
    }

}

private static void Swap(ArrayList<City>array,int Low, int High){
    City tempCtiy = array.get(Low);
    array.get(Low).set(array.get(High));
    array.get(High).set(tempCtiy);
}

此代码位于我的MST类中。所以当我运行它时

线程“main”中的异常java.lang.IndexOutOfBoundsException：索引：49，大小：49

它发生在这里：

    while (compareEdge.computeDistance() < MidDistance){
        Low += 1;
        compareEdge = new Edge(array.get(Low),city);
    }

帮我弄清楚什么是错的。我在VB.net上写的时候效果很好。

Answer 1

在while Low上添加终止条件，如下所示：

      while (compareEdge.computeDistance() < MidDistance &&
              && Low < array.size()-1){
              Low += 1;
              compareEdge = new Edge(array.get(Low),city);
      }

我的Quicksort不受约束

1 个答案: