Runtime error: addition of unsigned offset

Question

I was solving a question on Leetcode(Trapping rain water) and i wrote my solution which had been tested on my local machine as well as on GeeksForGeeks where it passed all TC's. the code is:

    int trap(vector<int>& height) {
        int size = height.size();
        int i,units;

        vector<int> l(size),r(size);
        l[0] = height[0];
        r[size-1] = height[size-1];

        for(i=1; i<size; i++){
            l[i] = max(height[i-1],l[i-1]);
        }

        for(i=size-1; i>=0; i--){
            r[i-1] = max(r[i],height[i]);
        }

        for(i=0; i<size; i++){
            if((min(l[i],r[i]) == 0) || (min(l[i],r[i])-height[i]<0))
                continue;
            else{
               units +=min(l[i],r[i])-height[i];
            }
        }
        return units;
    }

This is the only part i had to edit. And upon running it i'm getting the following error

Line 928: Char 34: runtime error: addition of unsigned offset to 0x6040000000d0 overflowed to 0x6040000000cc (stl_vector.h)
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /usr/bin/../lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8/bits/stl_vector.h:933:34

I need some help finding where I'm experiencing a buffer overflow. Cheers in advance.

Solution

It was a typo where it should have just been i>0 instead of i>=0.