gold_Job_Completion — USACO December_Contest
Task type: batch | Time limit: 2 s | Memory limit: 256 MB | Difficulty: 22
Algorithms: data structures, greedy, priority queue

Bessie the cow has $N$ ($1\le N\le 2\cdot 10^5$) jobs for you to potentially
complete. The $i$-th one, if you choose to complete it, must be started at or
before time $s_i$  and takes $t_i$ time to complete
($0\le s_i\le 10^{18}, 1\le t_i\le 10^{18}$).
What is the maximum number of jobs you can complete? Time starts at $0$, and
once you start a job you must work on it until it is complete, without starting
any other jobs in the meantime.
INPUT FORMAT (input arrives from the terminal / stdin):
The first line contains $T$, the number of independent test cases
($1\le T\le 10$). Each test case is formatted as follows.
The first line contains $N$.
Each of the next $N$ lines contains two integers $s_i$ and $t_i$. Row $i+1$ has
the details for the $i$th job.
It is guaranteed that the sum of $N$ over all test cases does not exceed
$3\cdot 10^5$.
OUTPUT FORMAT (print output to the terminal / stdout):
For each test case, the maximum number of jobs you can complete, on a new line.
SAMPLE INPUT:
3
2
1 4
1 2
2
2 3
1 2
3
1 4
2 3
1 2
SAMPLE OUTPUT:
1
2
2
For the first test case, you can only complete one of the jobs. After completing
one job, it will then be time $2$ or later, so it is too late to start the other
job, which must be started at time $1$ or earlier.
For the second test case,  you can start the second job at time $0$ and finish
at time $2$,  then start the first job at time $2$ and finish at time $5$.
SCORING:
Inputs 2: Within the same test case, all $t_i$ are equal.
Inputs 3-4: $N\le 2000$, $s_i, t_i\le 2000$
Inputs 5-8: $N\le 2000$
Inputs 9-16: No additional constraints.
Problem credits: Benjamin Qi

Starter code: