In this problem Can you explain me sample test case?How That answer comes.

both code did same.what is the difference?

First one : 
set <int> s;
s.insert (1);s.insert (3);s.insert (5);
auto tr = s.lower_bound (2);
s.erase (tr);<-----------here
--------------------------
Second one : 
set <int> s;
s.insert (1);s.insert (3);s.insert (5);
auto tr = s.lower_bound (2);
s.erase (*tr);<-----------here

In this problem.I tried greedy solution.But It didn't pass.I tried but I didn't find anti-test for my solution? Can you give me anti test for this code?

#include<bits/stdc++.h>
#define ll long long
using namespace std;
const int N = 5e5 + 5;
ll o, a[N], seg[N], sum;

int main () {
//	freopen("input.txt", "r", stdin);
	int n;
	cin >> n;
	for (int i = 1; i <= n; ++i) {
		cin >> a[i];
	}
	o++;
	seg[o] = a[1];
	for (int i = 2; i <= n; ++i) {
		sum = 0;
		int r;
		for (int j = i; j <= n; ++j) {
			sum += a[j];
			if (sum >= seg[o]) {
				r = j;
				break;
			}
		}
		if (sum >= seg[o]) {
			o++;
			seg[o] = sum;
			// i bilen r aralyk
			for (int j = i; j <= r; ++j) {
				if (seg[o] - a[j] >= seg[o - 1] + a[j]) {
					seg[o] -= a[j];
					seg[o - 1] += a[j];
				}
				else break;
			}
		}
		else {
			seg[o] += sum;
			break;
		}
		i = r;
	}
	cout << o << endl;
}

I'm trying to solve this problem about 3 days.Can you share your idea for subtasks.

If you has schedule or used to has schedule,Can you share?

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