find_if is not returning the expected output

Question

I am using find_if() to find the next higher value in a vector. It is returning the next index and not a higher value.

The input vector is:

vector<int> height = { 1,8,6,2,5,4,8,3,7 };

I am looking for the next highest value, starting at i=0, height[0] = 1. The code updates to set i=1, height[1] = 8. I expect to get i=7. I get i=2 instead.

for (size_t i = 0; i < height.size() - 1; i++)
{   
    auto res = std::find_if((height.begin() + i + 1), height.end(),
        [&height, i](int x) {           
        return height[x] >= height[i];
    });
    auto higher_index = std::distance(height.begin(), res);

    if (res != height.end() && higher_index < height.size())
    {
        // found the next highest height
        // calculate new area and make i the same as highest height
        area = min(height[i], height[higher_index]) * (higher_index - i);
        maxA = max(maxA, area);
        i = higher_index - 1;
    }
}

Answer 1

Your lambda should look like this

    [&height, i](int x) {           
        return x >= height[i];
    }

find_if passes the value of each element of the given sequence to the predicate. Not the index of each element.