CODEWITHSUNDEEP
c++vectorinsertiterator
santaman
santaman

Reputation: 3

C++ vector insert with Iterator is not working as I expected

C++11, Input is nums = [1,2,3,4,5]

void rotate(vector<int>& nums, int k) {
    nums.insert(nums.begin(), nums.end() - k, nums.end());
}

When k = 2, I expect this function should make nums to [4,5,1,2,3,4,5]
but it becomes [2,3,1,2,3,4,5]
When k = 1, nums is [4,1,2,3,4,5]
but when k = 4, nums is [2,3,4,5,1,2,3,4,5], which is what I wanted.
What am I doing wrong? Please help.

Upvotes: 0

Views: 345

Answers (1)

user17732522
user17732522

Reputation: 76678

The std::vector::insert overload that you are using has a precondition that neither the second nor the third argument are iterators into the vector itself.

You are violating that precondition and therefore your program has undefined behavior.

Upvotes: 2

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