c++ - 为什么我的程序会因大值而不是小值而导致程序崩溃？

Question

为什么我的程序会因大值而不是小值而崩溃？如果我输入 1-3，程序会执行它应该执行的操作，但是当我输入大于该值的数字时，程序会崩溃和/或无法完成？这与指针错误或我引用某些内容的方式有关吗？我不确定所以任何帮助表示赞赏。谢谢!

代码:

#include <iostream>
using namespace std;

void getData (int size, int *Arr){

    cout << "\n\nEnter integer data one line at a time\n" << endl ;

    for (int i=0; i < size; i++){
        cin >> Arr[i];
    }
}

void findMinAndMax(int array[], int size, int *min, int *max) {

    int smallest = array[0];
    int largest = array[0];

    *min = smallest;
    *max = largest;

    for (int i = 1; i < size; i++)
        {
            if (array[i] > *max){
                *max = array[i];
                cout << "Max Value (loop): " << *max << endl;
            }
            if (array[i] < *min){
                *min = array[i];
                cout << "Min Value (loop): " << *max << endl;
            }
        }

    // testing code
    cout << "Min Value: " << *min << endl;
    cout << "Max Value: " << *max << endl;

}

int *makeFrequency (int data[], int dSize, int *minDataValue, int *maxDataValue) {

    cout << "Min Value Pre: " << *minDataValue << endl;// testing code
    cout << "Max Value Pre: " << *maxDataValue << endl;// testing code
    findMinAndMax(data, dSize, minDataValue, maxDataValue);
    cout << "Min Value Post: " << *minDataValue << endl; // testing code
    cout << "Max Value Post: " << *maxDataValue << endl;// testing code


    int fSize = *minDataValue + *maxDataValue;

    cout << "fSize: " << fSize << endl; // testing code

    int *frequency;
    frequency = new int [fSize];

    // if frequency is 0, end
    if (frequency == 0)
        {
            return 0;
        }

    // set all elements to 0 in array frequency
    for (int i = 0; i <= fSize; i++) {
        frequency[i] = 0;
    }


    for (int i = 0; i <= dSize; i++) {
        int j = data[i] - (*minDataValue) + 1;
        frequency[j] = frequency[j] + 1;
    }

    return frequency;
}

void makeHistogram (int *freq, int min, int max ){

    cout << "Frequency Value HISTOGRAM: " << *freq << endl;

    cout << "\n\n\n ----------- Histogram ----------------\n" << endl;

    int size = min + max;
    cout << "Size Value HISTOGRAM: " << size << endl;

    for (int i = 0; i < size; i++){

        if (freq[i] > 0) {

            cout << "\n" << min + i - 1 << ": ";

            for (int j = 0; j < freq[i]; j++) {
                cout << '*';
            }
        }
    }
    cout << endl << endl;
}

int main() {

    int dSize;
    int *ArrayOfInts;

    cout << "How many data values? ";
    cin >> dSize;

    ArrayOfInts = new int [dSize];

    getData(dSize, ArrayOfInts);


    int *frequency, min, max;

    frequency = makeFrequency(ArrayOfInts, dSize, &min, &max);

    if (frequency == 0) return -1;

    cout << "Min Value MAIN: " << min << endl; // testing code
    cout << "Max Value MAIN: " << max << endl; // testing code
    cout << "Frequency Value MAIN: " << *frequency << endl;

    makeHistogram(frequency, min, max);


    delete [] frequency;

    return 0;
}

Answer 1

一个地方你有可能导致崩溃的未定义行为:

在这里你分配fSize元素:

frequency = new int [fSize];

稍后您迭代它直到 fSize :

for (int i = 0; i <= fSize; i++) {

你应该改成i < fSize ，因为您的数组中没有 fSize 元素。 i <= dSize 也有同样的问题稍后的。应该是i < dSize .

顺便说一句。我不明白为什么只有大值才会导致代码崩溃，也许这只是 UB。