CODEWITHSUNDEEP
c++
Bowen Peng
Bowen Peng

Reputation: 1815

vector iterator not incrementable, which is related to the operation of iterator and erase

I am searching for a long time on net. But no use. Please help or try to give some ideas how to solve this problem.

class Solution{
public:
    int removeElement(vector<int> &nums, int val)
    {

        for (auto &it = nums.begin(); it != nums.end(); ++it)
        {
            if (*it == val)
            {
                it = nums.erase(it);
            }
        }
        return nums.size();
    }
};
int main(void)
{
    Solution s; 
    vector<int> vi = { 3, 2, 2, 3 };
    cout << "size = " << s.removeElement(vi, 3) << endl;
    for (auto &i : vi)
    {
        cout << i << " ";
    }
    cout << endl;

    return 0;
}

which are the class body and main function body of my code. But when i run it, compiler popped a window:

enter image description here

Upvotes: 0

Views: 696

Answers (1)

MikeCAT
MikeCAT

Reputation: 75062

After erasing the last element, it becomes nums.end() and incrementing it is not allowed.

You shouldn't increment it after erasing. This will also fix problem that one element is skipped after erasure.

Also the & in auto &it = nums.begin() should be removed because having it will make it invalid initialization of non-const reference.

Try this:

#include <iostream>
#include <vector>

using std::vector;
using std::cout;
using std::endl;

class Solution{
public:
    int removeElement(vector<int> &nums, int val)
    {

        for (auto it = nums.begin(); it != nums.end();)
        {
            if (*it == val)
            {
                it = nums.erase(it);
            } else
            {
                ++it;
            }
        }
        return nums.size();
    }
};
int main(void)
{
    Solution s; 
    vector<int> vi = { 3, 2, 3, 3, 2, 3 }; // added testcase of consecutive 3
    cout << "size = " << s.removeElement(vi, 3) << endl;
    for (auto &i : vi)
    {
        cout << i << " ";
    }
    cout << endl;

    return 0;
}

Upvotes: 2

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