|| ||Code Submission Evaluation System
CSES Problem Set
Flight Routes Check
Task | Statistics
CSES - Flight Routes CheckCSES - Flight Routes Check
|Time limit:||1.00 s
||Memory limit:||512 MB|
There are $n$ cities and $m$ flight connections. Your task is to check if you can travel from any city to any other city using the available flights.
The first input line has two integers $n$ and $m$: the number of cities and flights. The cities are numbered $1,2,\dots,n$.
After this, there are $m$ lines describing the flights. Each line has two integers $a$ and $b$: there is a flight from city $a$ to city $b$. All flights are one-way flights.
Print "YES" if all routes are possible, and "NO" otherwise. In the latter case also print two cities $a$ and $b$ such that you cannot travel from city $a$ to city $b$.
- $1 \le n \le 10^5$
- $1 \le m \le 2 \cdot 10^5$
- $1 \le a,b \le n$