3229. Minimum Operations to Make Array Equal to Target

You are given two positive integer arrays nums and target, of the same length.

In a single operation, you can select any subarray of nums and increment or decrement each element within that subarray by 1.

Return the minimum number of operations required to make nums equal to the array target.

struct MergeInterval {
    map<int,int> range;
    void add(int x) {
        auto it = range.upper_bound(x);
        if(it != begin(range) and prev(it)->second + 1 == x) {
            --it;
        } else {
            range[x] = x;
            it = range.lower_bound(x);
        }
        it->second = max(it->second, x);
        while(next(it) != end(range) and it->second + 1 == next(it)->first) {
            it->second = next(it)->second;
            range.erase(next(it));
        }
    }
};
class Solution {
    long long helper(map<int,vector<int>>& mp) {
        mp[0].push_back(0);
        long long res = 0;
        MergeInterval mi;
        for(auto it = begin(mp); it->first != 0; it++) {
            for(auto& at : it->second) mi.add(at);
            res += mi.range.size() * (next(it)->first - it->first);
        }
        return res;
    }
public:
    long long minimumOperations(vector<int>& nums, vector<int>& target) {
        long long n = nums.size();
        map<int,vector<int>> pos, neg;
        for(int i = 0; i < n; i++) {
            int x = nums[i] - target[i];
            if(x > 0) pos[-x].push_back(i);
            else if(x < 0) neg[x].push_back(i);
        }
        return helper(pos) + helper(neg);
    }
};