Question

所以我编写了自己的ArrayList实现（也就是C ++中的向量），并且我用它包含了几个算法。现在我的合并排序方法似乎是在泄漏内存，但我已逐行检查代码，跟踪分配到删除，这一切看起来都很顺利！

我应该注意，我有一个测试脚本，用于ArrayList中的每个方法，然后我崩溃，然后我尝试删除mergesort测试，并且繁荣，不再崩溃。但有趣的是......它不会一直崩溃，它有时会起作用，而且会使其他人崩溃。

这两种方法的代码如下：

快速变量枚举：

array =支持arrayList的数组

size =一个用于跟踪数组大小的int。

sorted =一个布尔值，指示列表是否已排序

/**
 * Runs merge sort on this ArrayList<T>. Interface function to the central,
 * recursive, merge sort function.
 *
 * Runs in O(nlogn) time. However it consumes extra memory.
 */
template<class T>
void ArrayList<T>::mergeSort() {

    T* temp = mergeSort(array, size);
    delete [] array;
    array = temp;
    sorted = true;
}

/**
 * Runs merge sort on the passed in array. Recursive.
 *
 * Runs in O(nlogn) time. However it consumes extra memory.
 *
 * @param array the array to sort.
 * @param arraySize the size of the array that is to be sorted.
 * @return the sorted array.
 */
template<class T>
T* ArrayList<T>::mergeSort(T* array, int arraySize) {

    T* returnArray;

    //If the array is more than one element.
    if (arraySize > 1) {

        int size1 = arraySize / 2;
        int size2 = arraySize - size1;

        T* array1;
        T* array2;

        //Recurse.
        array1 = mergeSort(array, size1);
        array2 = mergeSort(array + size1, size2);

        //Allocate memory for return array.
        returnArray = new T[arraySize];

        //Loop through all elements in returnArray.
        int i = 0, j = 0, k = 0;
        while (i < arraySize) {

            //Place the lesser of two elements in returnArray.
            if ((array1[j] <= array2[k] && j < size1)
                    || k == size2) {

                returnArray[i] = array1[j];
                j++;
            }
            else {

                returnArray[i] = array2[k];
                k++;
            }

            i++;
        }

        //Free the memory allocated in the recursive calls.

        delete [] array1;
        delete [] array2;
        array1 = 0;
        array2 = 0;
    }
    //If one element is in the passed array.
    else {

        //Allocate memory for new array, and assign passed value to it.
        //This is done so delete can be called in the calling function.
        returnArray = new T[1];
        returnArray[0] = array[0];
    }

    return returnArray;
}

Answer 1

您在检查array1 [ j ]之前是否正在访问j < size1。如果j >= size1那么访问该索引处的数组是非法的。它可能并不总是崩溃，具体取决于堆中内容的内存布局，但有时会崩溃。你的支票应该是这样的：

if (((j < size1) && (array1[j] <= array2[k])) || k == size2) {
...

我的记忆泄漏在哪里？

1 个答案: