调试断言失败。C++ 向量下标超出范围
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Debug assertion failed. C++ vector subscript out of range
提问by Abhishek Jain
the following code fills the vector with 10 values in first for loop. in second for loop i want the elements of vector to be printed. The output is till the cout statement before the j loop.Gives error of vector subscript out of range.
以下代码在第一个 for 循环中用 10 个值填充向量。在第二个 for 循环中，我希望打印向量的元素。输出直到 j 循环之前的 cout 语句。给出向量下标超出范围的错误。
#include "stdafx.h"
#include "iostream"
#include "vector"
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{ vector<int> v;
cout<<"Hello India"<<endl;
cout<<"Size of vector is: "<<v.size()<<endl;
for(int i=1;i<=10;++i)
{
v.push_back(i);
}
cout<<"size of vector: "<<v.size()<<endl;
for(int j=10;j>0;--j)
{
cout<<v[j];
}
return 0;
}
回答by BartoszKP
Regardless of how do you index the pushbacks your vector contains 10 elements indexed from 0(0, 1, ..., 9). So in your second loop v[j]is invalid, when jis 10.
无论您如何索引推回，您的向量都包含从0( 0, 1, ..., 9)索引的 10 个元素。所以在你的第二个循环中v[j]是无效的， when jis 10。
This will fix the error:
这将修复错误：
for(int j = 9;j >= 0;--j)
{
cout << v[j];
}
In general it's better to think about indexes as 0based, so I suggest you change also your first loop to this:
一般来说，最好将索引视为0基础，因此我建议您也将第一个循环更改为：
for(int i = 0;i < 10;++i)
{
v.push_back(i);
}
Also, to access the elements of a container, the idiomatic approach is to use iterators (in this case: a reverse iterator):
此外，要访问容器的元素，惯用的方法是使用迭代器（在这种情况下：反向迭代器）：
for (vector<int>::reverse_iterator i = v.rbegin(); i != v.rend(); ++i)
{
std::cout << *i << std::endl;
}
回答by billz
vhas 10element, the index starts from 0to 9.
v有10元素，索引从0到9。
for(int j=10;j>0;--j)
{
cout<<v[j]; // v[10] out of range
}
you should update forloop to
你应该将for循环更新为
for(int j=9; j>=0; --j)
// ^^^^^^^^^^
{
cout<<v[j]; // out of range
}
Or use reverse iteratorto print element in reverse order
或者使用反向迭代器以相反的顺序打印元素
for (auto ri = v.rbegin(); ri != v.rend(); ++ri)
{
std::cout << *ri << std::endl;
}
回答by suraj kumar
this type of error usually occur when you try to access data through the index in which data data has not been assign. for example
当您尝试通过尚未分配数据数据的索引访问数据时，通常会发生此类错误。例如
//assign of data in to array
for(int i=0; i<10; i++){
arr[i]=i;
}
//accessing of data through array index
for(int i=10; i>=0; i--){
cout << arr[i];
}
the code will give error (vector subscript out of range) because you are accessing the arr[10] which has not been assign yet.
该代码将给出错误（向量下标超出范围），因为您正在访问尚未分配的 arr[10]。
