https://code.google.com/codejam/contest/3214486/dashboard
Simple problem.
Just check for all start time and all possible broken LED sets.
Simple problem. Brute force is enough.
Be care of 2 2 4 4.
A hard problem. Very hard to implement.
For each variable, try to write it to ax+b, where a is flag (1/-1), b is a constant,
x is a variable (unionFind-find/bfs).
Then check if each variable can be calculated.
Finally, check if we can calculate (ax+b)+(cy+d).(Iff x and y both can be calculated, or x=y and a+c=0.)
Be careful of these cases:
a+a=3, b+b=4 => a+b=3.5 (output 3).
Check my code C.java for more details. A really hard problem.
Greedy problem. For each tile, try to cut it to satisfy tiles as much as possible.
Harder than A/B, but easier than C, I think.