Question

编辑：问题已解决，由于不正确的while（）条件，我正在访问尚未初始化的数据。我已将其从“或”更改为“与”。现在，它可以按预期工作。谢谢！

我试图在C ++中找到两个数组之间的交集。我已经编写了满足我需要的代码，但是当我删除[]数组时，它会中断，从而导致浮点异常。（除以零？）如何保存所需的值，而又不会导致程序中的内存泄漏？

如果我省略delete []语句，此代码将按照我的预期工作，但我相信这会导致内存泄漏。如果我省略语句greatIntersection = *（factorsa + i），它将返回1；我该怎么做才能将值保存在factora + i并随后删除该数组以避免内存泄漏？

const int Fraction::findgcf(int a, int b) const{
    a = std::abs(a); //absoute value
    b = std::abs(b);

    int* factorsa = new int[a]; //dynamic array of ints to store factors of a
    int* factorsb = new int[b]; //dynamic array of ints to store factors of b


    int numFactorsa = 0;
    for(int i = 1; i <= a; i++){//iterate over the ints from 1 to a
        if(a % i == 0) {//if we find a factor of a
            *(factorsa + numFactorsa) = i;// and append that to the array
            numFactorsa++;
        }

    }

    int numFactorsb = 0;
    for(int i = 1; i <= b; i++){
        if(b % i == 0){
            *(factorsb + numFactorsb) = i;
            numFactorsb++;
        }
    }

    int biggestIntersection = 1;

     int i = 0, j = 0;
    while(i < numFactorsa || j < numFactorsb){//while we are in the bounds of the two arrays
        if(*(factorsa + i) < *(factorsb + j)){ //if the factor of a is less than the factor of b
            i++;                               //move the index of a up one
        } else if (*(factorsa + i) > *(factorsb + j)){ //if the factor of b is less than the factor of a
            j++;                                       //move the index of b up one
        } else {                                    //otherwise they must be equal
            biggestIntersection = *(factorsa + i); //so that is the new biggest intersection between the sets
            i++; j++;
        }
    }

    delete [] factorsa;
    delete [] factorsb;
    return biggestIntersection;

Answer 1

您确实应该使用std :: vector。这样您就不必担心清理了。

const int Fraction::findgcf(int a, int b) const{
    a = std::abs(a); //absoute value
    b = std::abs(b);

    std::vector<int> factorsa(a);
    std::vector<int> factorsb(b);

    int numFactorsa = 0;
    for(int i = 1; i <= a; i++){//iterate over the ints from 1 to a
        if(a % i == 0) {//if we find a factor of a
            factorsa[numFactorsa] = i;// and append that to the array
            numFactorsa++;
        }

    }

    int numFactorsb = 0;
    for(int i = 1; i <= b; i++){
        if(b % i == 0){
            factorsb[numFactorsb] = i;
            numFactorsb++;
        }
    }

    int biggestIntersection = 1;

    int i = 0, j = 0;
    while(i < numFactorsa || j < numFactorsb){//while we are in the bounds of the two arrays
        if(factorsa[i] < factorsb[j]){ //if the factor of a is less than the factor of b
            i++;                               //move the index of a up one
        }
        else if (factorsa[i] > factorsb[j])
        {                                              //if the factor of b is less than the factor of a
            j++;                                       //move the index of b up one
        } else {                                    //otherwise they must be equal
            biggestIntersection = factorsa[i];      //so that is the new biggest intersection between the sets
            i++; j++;
        }
    }

    return biggestIntersection;
}

Answer 2

最大的问题-尽管可能是一个最小的例子，但可能导致错误的原因是，您正在访问的内存尚未初始化。这可能会导致无法预测的行为。

int* factorsa = new int[a];不会将该数组中的每个int设置为零-数组的内容实际上可以是任何内容。稍后，在第一个for循环中，您确实为某些数组位置（而不是全部）设置了值。因此，在最后的for循环中，您无法知道要输出的内容。这将取决于您要求new提供的存储位置的大致随机内容。

（此外，如注释所示，您的while循环条件是错误的。）

如何在C ++中从动态数组保存值？

2 个答案: