Your solution is simply amazing!!! I spent an whole hour scratching my head thinking about disjoint sets!! Here I what wrote it in C++ using map better allocation.

define ll long long int

using namespace std;

int main() { ll n,m,a,b,k; cin>>n>>m; map arr; while(m--){ cin>>a>>b>>k; if(arr.find(a)==arr.end()) arr[a]=0; arr[a]+=k; if(arr.find(b)==arr.end()) arr[b]=0; arr[b+1]-=k; } ll max=0,x=0; map::iterator i; for(i=arr.begin();i!=arr.end();i++){ x+=i->second; if(x>max){ max=x; } } cout<

Thanks man!! I was thinking to quit but your answer gave me spirit to keep continuing.