OJ Board

Also, I'm not sure you would want to use more advanced C++ features anyway, as I believe they will be unnecessarily slow because the compile with optimizations turned off. There are for instance several problems at UVA where you will time out if you use STL vector (without actually using the dynamic...

A pointer is simple an integer. When you do ptr=&b[4], ptr will contain the address to the fourth element in b, which is just a number. When you later free the b array, the value in ptr will of course not change - it will still contain the same number. However, now this pointer points to memory ...

The result of the first and last input is correct, but the second one is not a valid input. If your program actually gets an answer for that in any case, it's a bit strange, it should be infinite or something in that case.

There are no tricks in the problem nor the input really.

Ohhh... I guess I've never thought about that. Thanks

This is the basic brute-force method which works on basically all game theory problems where you can enumerate all states of the game: 1. Start by finding all final states and mark them as a win or a loss and put these states in a queue (in 10404, that would be marking 0 as a loss) 2. Pop the front ...

You start with the original sieve algorithm, like this: char isprime[MAX]; for(int i=0;i<MAX;i++) isprime =i>=2; for(int i=2;i<MAX;i++) if (isprime ) // i is a prime, so make all multiples of it non-prime for(int j=i*2;j<MAX;j+=i) isprime[j]=0; Then you realize you can store the data more compact si...

Umm, complexity doesn't matter on input size. In any case, do you have any reference to that algorithm?

This is problem 108 as I'm sure you know, and I'm pretty certain it is a well established fact that you can't, in the general case, solve this faster than N^3. I'm afraid I have no idea how to prove this, but it seems like a standard problem so I think I should have heard if there's a N^2 solution.

There's no need to simulate the ball. Since you know the number of horizontal and vertical bounces, you know how far the ball has travelled in the horizontal and vertical direction. Just use pythagoras formula and divide with the ball speed.

14 7 8 12 4 5 1 6 11 2 3 10 9 13 14 7 8 4 5 2 3 12 1 6 10 14 11 9 13 5 5 4 3 2 1 5 4 3 2 1 Try this. My (AC) program returns 1: 2: 3: 4: 5: 2 3 6: 10 7: 8 12 8: 4 5 9: 10: 14 11: 9 13 12: 1 6 11 13: 14: 1: 2: 3: 4: 5: 1 2 3 4 After I solved this problem in the contest, I noticed my program was wron...

My memory-tight sieve looks like this: #define MAXSIEVE 100000000 // All prime numbers up to this #define MAXSIEVEHALF (MAXSIEVE/2) #define MAXSQRT 5000 // sqrt(MAXSIEVE)/2 char a[MAXSIEVE/16+2]; #define isprime(n) (a[(n)>>4]&(1<<(((n)>>1)&7))) // Works when n is odd int i,j; memset(a,255,si...

Huh?? c can get as big as 1693182318746371!! For a list of all maximal prime gaps, check out

http://www.utm.edu/research/primes/notes/GapsTable.html

Of course, I don't think that will help you very much in solving the problem...

I wouldn't care too much about the low execution times some people get on some problems. In most cases this is either due some really crazy optimizations (like using inline assembly and tweaking input/output) or really big precalculated lookup tables. There are some people who seem to take a big del...

I simply calculate the volume below the three triangles, {a,b,c}, {b,d,c} and {c,d,(0,0,1)}. I never managed to get the answer in the sample output, no matter how I changed the order of triangles or permuted a,b,c,d.

But the problem description is just awful.

I just wanted to point out that the sample output in this problem is wrong, it should be

2 336.83

Not many have submitted on this one, maybe it's because of this (?)