C++ 抛出“std::out_of_range”实例后调用终止
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terminate called after throwing an instance of 'std::out_of_range'
提问by Costas Vrahimis
Why does this happen my program says that it has no errors but then when I run it I get terminate called after throwing an instance of 'std::out_of_range' what(): vector:_M_range_check. I am new to c++ so I don't understand these errors
为什么会发生这种情况，我的程序说它没有错误，但是当我运行它时，我在抛出一个 'std::out_of_range' what(): vector:_M_range_check 实例后被调用终止。我是 C++ 新手，所以我不明白这些错误
#include <vector>
#include <iostream>
#include <random>
#include <time.h>
using namespace std;
using std::vector;
int main()
{
vector<int> deck;
vector<int> nums;
default_random_engine eng(time(0));
uniform_int_distribution<int> dis(0, 51);
int pos1;
int pos2;
int num1;
int num2;
int i;
int n;
int m;
for (i = 0; i < 52; i++)
{
nums.push_back(i);
}
for(int j = 0; j < 52; j++)
{
cout << nums.at(i) << "\n";
}
for(n = 0; n < 50; n++)
{
pos1 = dis(eng);
pos2 = dis(eng);
cout << pos1 << "\n" << pos2 << "\n";
num1 = deck.at(pos1);
num2 = deck.at(pos2);
}
}
回答by Martin J.
It looks to me as if this is due to a typo, and you should use the variable 'j' in the second loop. After the first loop,
在我看来，这是由于打字错误造成的，您应该在第二个循环中使用变量“j”。第一次循环后，
for (i = 0; i < 52; i++)
{
nums.push_back(i);
}
the variable 'i' contains the value 52, so it sounds expected that calling nums.at(i) would throw a std::out_of_range, since nums only contains 52 values, starting at index 0.
变量“i”包含值 52，因此听起来预期调用 nums.at(i) 会抛出 std::out_of_range，因为 nums 仅包含 52 个值，从索引 0 开始。
for(int j = 0; j < 52; j++)
{
cout << nums.at(i) << "\n";
}
Fix it by replacing the argument of at() with 'j', which I assume was the original intent:
通过将 at() 的参数替换为 'j' 来修复它，我认为这是原始意图：
for(int j = 0; j < 52; j++)
{
cout << nums.at(j) << "\n";
}
回答by juanchopanza
You access elements in deckhere:
您可以访问deck此处的元素：
num1 = deck.at(pos1);
num2 = deck.at(pos2);
but it is empty. You have to fill it at some point before making those calls. You can check if a vector is empty with the std::vector::emptymethod, and get it's size with std::vector::size. See this std::vectorreferencefor more information on those two methods.
但它是空的。在拨打这些电话之前，您必须在某个时候填写它。您可以使用该std::vector::empty方法检查向量是否为空，并使用std::vector::size. 有关这两种方法的更多信息，请参阅此std::vector参考资料。
