c++ leetcode 525 contiguous array solution

code >>

class Solution {
public:
    int findMaxLength(vector<int>& nums) {
 
        const int numSize = (int)nums.size();
        unordered_map<int, vector<int>> hashMap;
        
        int result = 0;
        hashMap[0].emplace_back(-1);
        int accum = 0;
        for (int i = 0; i < numSize; i++)
        {
            if (nums[i] == 0)
            {
                accum = accum + -1;
                hashMap[accum].push_back(i);
            }
            else
            {
                accum = accum + 1;
                hashMap[accum].push_back(i);
            }
 
        }
        
        for (const auto& ind_hash : hashMap)
        {
            int diff = ind_hash.second.back() - ind_hash.second.front();
            if (diff > result)
                result = diff;
        }
 
        return result;
    }
};