H. The Third Lettertime limit per test2 secondsmemory limit per test256 megabytesinputstandard inputoutputstandard outputIn order to win his toughest battle, Mircea came up with a great strategy for his army. He has n soldiers and decided to arrange them in a certain way in camps. Each soldier has to belong to exactly one camp, and there is one camp at each integer point on the x-axis (at points \cdots, -2, -1, 0, 1, 2, \cdots).The strategy consists of m conditions. Condition i tells that soldier a_i should belong to a camp that is situated d_i meters in front of the camp that person b_i belongs to. (If d_i < 0, then a_i's camp should be -d_i meters behind b_i's camp.)Now, Mircea wonders if there exists a partition of soldiers that respects the condition and he asks for your help! Answer "YES" if there is a partition of the n soldiers that satisfies all of the m conditions and "NO" otherwise.Note that two different soldiers may be placed in the same camp.InputThe first line contains a single integer t (1 \leq t \leq 100) — the number of test cases.The first line of each test case contains two positive integers n and m (2 \leq n \leq 2 \cdot 10^5; 1 \leq m \leq n) — the number of soldiers, and the number of conditions respectively.Then m lines follow, each of them containing 3 integers: a_i, b_i, d_i (a_i \neq b_i; 1 \leq a_i, b_i \leq n; -10^9 \leq d_i \leq 10^9) — denoting the conditions explained in the statement. Note that if d_i is positive, a_i should be d_i meters in front of b_i and if it is negative, a_i should be -d_i meters behind b_i.Note that the sum of n over all test cases doesn't exceed 2 \cdot 10^5.OutputFor each test case, output "YES" if there is an arrangement of the n soldiers that satisfies all of the m conditions and "NO" otherwise.ExampleInput
45 31 2 22 3 44 2 -66 51 2 22 3 44 2 -65 4 43 5 1002 21 2 51 2 44 11 2 3Output
YES
NO
NO
YES
NoteFor the first test case, we can partition the soldiers into camps in the following way: soldier:  Soldier 1 in the camp with the coordinate x = 3.  Soldier 2 in the camp with the coordinate x = 5.  Soldier 3 in the camp with the coordinate x = 9.  Soldier 4 in the camp with the coordinate x = 11. For the second test case, there is no partition that can satisfy all the constraints at the same time.For the third test case, there is no partition that satisfies all the constraints since we get contradictory information about the same pair.For the fourth test case, in order to satisfy the only condition, a possible partition is:  Soldier 1 in the camp with the coordinate x = 10.  Soldier 2 in the camp with the coordinate x = 13.  Soldier 3 in the camp with the coordinate x = -2023.  Soldier 4 in the camp with the coordinate x = -2023. 
45 31 2 22 3 44 2 -66 51 2 22 3 44 2 -65 4 43 5 1002 21 2 51 2 44 11 2 3
YES NO NO YES 
['dfs and similar', 'dsu', 'graphs', 'greedy', 'implementation', '*1700']