C++中使用迭代器的子数组/向量会导致崩溃

Question

我写了一段代码，从这个[示例解决方案][1]中使用Iterator打印所有子数组[1] ：https://stackoverflow.com/questions/421573/best-way-to-extract-a-subvector-from-a-vector

void printarray(std::vector<int> array) {
for (auto a : array) {
std::cout << a <<" ";
}
std::cout<< std::endl;
}
void subArrayPrinter(vector<int>& arr) {
for (int i = 0; i < arr.size(); i++) {
for (int j = 2; j <= arr.size(); j++) {
std::vector<int> newVec(arr.cbegin() + i, arr.cbegin() + j);
printarray(newVec);
}
}
}
int main() {
std::vector<int> zarray = {23, 2, 4, 6, 7};
std::cout << subArrayPrinter(zarray) << std::endl;
}

例如[23，2，4，6，7]我最终看到一个崩溃，它抱怨末端的阵列太大

o/p

23 2 4 6 7 
23 2 
23 2 4 
23 2 4 6 
23 2 4 6 7 
2 
2 4 
2 4 6 
2 4 6 7 
// <- the array size is zero here, but didnt see this for the first sub array case 
4 
4 6 
4 6 7 
terminate called after throwing an instance of 'std::length_error'
what():  cannot create std::vector larger than max_size()
Aborted (core dumped)

我检查了gdb，由于某种原因，数组大小变得巨大

Answer 1

在内部循环中将i分配给j，您将看到您所期望的：

void subArrayPrinter(vector<int>& arr) {
for (int i = 0; i < arr.size(); i++) {
for (int j = i; j <= arr.size(); j++) {
std::vector<int> newVec(arr.cbegin() + i, arr.cbegin() + j);
printarray(newVec);
}
}
}
int main() {
std::vector<int> zarray = {23, 2, 4, 6, 7};
std::cout << "Begin " << endl;
subArrayPrinter(zarray);
}

Outuput:

Begin 
23 
23 2 
23 2 4 
23 2 4 6 
23 2 4 6 7 
2 
2 4 
2 4 6 
2 4 6 7 
4 
4 6 
4 6 7 
6 
6 7 
7 

Answer 2

As@KamilCuk正确地指出了代码中的问题。崩溃的原因是i > j时分配了新的矢量。可能您需要将内部for循环更改为

for (int j = i + 1; j <= arr.size(); j++)