for loop done without meeting the condition I set - c++

Question

#include <iostream>
#include <vector>
using namespace std;
int main()
{
int n = 5;
int nums[] = {0 ,1};
if (n == 0)
{
return 0;
} else if (n == 1)
{
return 1;
} else{
for (int i = 2; i < n + 1; i++)
{
cout << i << endl;
nums[i] = nums[i-2] + nums[i-1];
}
return nums[n]
}
return 0;
}
It is just a simple fibonacci array, but my code only gives stdout one time and it is two. FYI: this code may not be correct to compute the nth term of fibonacci array, but i am strugglling with this for loop.
I think the condition of i < n+1 is not meet, but why this for loop ends

Answer 1

nums[i] has size 2. You can't access nums[i] for i >= 2. An array doesn't grow. You can't change the size of an array. Use a std::vector. You've already included the header. A return statement finishes a function. In case of the main function it causes the program to stop. The return value of the main function by convention describes if the program was successful or errors occurred. You are returning
return nums[n];
That's probably not your intention. I assume you want to print the vector.
#include <iostream>
#include <vector>
using namespace std;
int main()
{
int n = 5;
std::vector<int> nums {0 ,1};
if (n == 0)
{
return 0;
} else if (n == 1) {
return 1;
} else {
nums.reserve(n + 1);
for (int i = 2; i < n + 1; i++)
{
cout << i << '\n';
nums.emplace_back(nums[i-2] + nums[i-1]);
}
for (const auto num : nums)
{
cout << num << '\n';
}
}
return 0;
}

Answer 2

it's because you can't access to nums[2] so the correct version of your code is :
#include <iostream>
#include <vector>
using namespace std;
int main()
{
int n = 5;
int nums[5] = {0 ,1};
if (n == 0)
{
return 0;
} else if (n == 1)
{
return 1;
} else{
for (int i = 2; i < n + 1; i++)
{
cout << i << endl;
nums[i] = nums[i-2] + nums[i-1];
}
return nums[n]
}
return 0;
}

Answer 3

you must provide estimated size to array or you will create vector or some dynamic array..
Your approach always give Segmentation fault;
#include <iostream>
#include <vector>
using namespace std;
int main()
{
int n = 5;
vector<int> nums(n+1);
nums[0]=0;
nums[1]=1;
if (n == 0)
{
return 0;
} else if (n == 1)
{
return 1;
} else{
for (int i = 2; i < n + 1; i++)
{
// cout << i << endl;
nums[i] = nums[i-2] + nums[i-1];
}
for(int i=0;i<n;i++)
{
cout<<nums[i]<<endl; }
}
return 0;
}
*/