Dear meeeep,

Edit: In your example, 50 goods are transferred from cities 0 and 1 to 2. Then there will be 100 goods in each city — my code covers this sample case.

But I have made an example, which will break my code:

3 2
3 1 0
0 0 4

Here, 3 goods will be transferred to 2-nd city: 2 from 0-th, and 1 from 1-st.

A better way is to move 1 unit of good from 0-th to 1-st city, and then move 2 goods from cities 0 and 1 to city 2, that is 4 goods in total.

I supposed that there should be only direct transfers, that the same goods couldn't be transferred from city 1 to city 3 via city 2.

Hope to read the description more thoroughly and do better next time.

Problem E. Goods transportation — Why is this O(n*n) approach incorrect?

0.1. i goes from n-1 to 0:

1.1. trans = min(prods[i], sells[i]); // Sell as much as possible at the current i-th city.

ans += trans; sells[i] -= trans;

1.2. j goes from i-1 down to 0:

trans = min(sells[i], c, prods[j]); // Transfer as much as possible from the j-th city.

ans += trans; prods[j] -= trans; sells[i] -= trans;

1.3. Output the ans.

You are right. I was thinking of writing about this in a separate post tomorrow, but you were the first to bring it up! Consider a connected graph on 4 vertices: a,b,s,t. Edges: as, at, bs, bt. Using edges as, bs implies that either at or bt must be used. Thus the citation "or with both of them (only if we have in the graph an edge {s, t})" is not (!) valid meaning that the example above does not have an edge between s and t, yet both s and t must be used. I wonder whether this situation is covered in the system tests?

First, let's notice that problem is Div2F, not E. I guess it was meant, that at the end the graph is restored(!) by getting back s, t, and all the deleted edges if any. After step 2, vertices s and t will belong to the two spanning trees. Assume s and t in the same component; otherwise we are done. These two spanning trees should be linked to the remaining components as well as to each other either directly or indirectly.

To see someone's submissions, go to user's profile Dabagh, and click the SUBMISSIONS menu item.

If you insert an extra border of water(`.'), presenting an ocean, around 4 sides of the area, there will be no runtime errors as "i" can go from 0 to n+1, and j from 0 to m+1. First of all, visit the (0,0) which is the ocean, then proceed with the main area. http://mirror.codeforces.com/contest/723/submission/21156099

I spent some time on solving C, then decided to solve D first, and then returned back to C. What do you do if you do not have full understanding of a problem?

Here is a good article, explaining segment tree, at codeforces

Visit clist.by

hacking is open...

Each problem e.g. http://mirror.codeforces.com/contest/704/problem/D usually has a tag attached (flows in this case), but it is not possible to filter by the tag from the problem's page. To apply the filter, one may go to http://mirror.codeforces.com/problemset, and click the tag e.g. http://mirror.codeforces.com/problemset/tags/flows Q1. I wonder is there a better way to filter by a tag? Q2. I wanted to solve at least one problem per each tag — is there a list of all tags?

It looks like the issue is the same — please see my comment above http://mirror.codeforces.com/blog/entry/46450?#comment-309097

Event 3 is processed incorrectly: the fact that there are some unread application x events (byApp(x) > 0) does not imply that those events are among the first t events. E.g. given 3 4 1 1 2 1 1 1 3 1, your code will delete the second addition event "1 1" whereas it should not have.

Consider this example, where the last monster (5, 0) is unreachable: 2 3 1 0 3 0 2 0 4 0 5 0

Your code finds some interval, not necessarily the shortest one. Consider an example: 8 abcaabbc Your code will first move l from 0 to 4, leaving r=7, and then stop on "abbc" getting 4 whereas the returned value should be 3 (the first three letters "abc").

In problem B, "d contains no trailing zeros" could basically mean that d can have leading 0s. For example, 0.0001e1 should be printed as 0.001; 0.01e2 as 1; 0.01e5 as 1000; and 1.02e5 as 102000.

A man, having a blue belt, says "I don't know nothing." Who would believe you?
And you participate in programming contests to achieve what? What is really bothering you?

As for me, it makes me a better coder because almost every contest I learn something new, polish my skills, encounter interesting problems that raise beyond my current job level. Also, when I look at the code of the world best programmers, I see that still there so are many things I have to put to my pocket.

Basically, Programming consists of Algorithms, Technologies, Software Engineering. Maybe, you should take a break, write your own piece of software.
Good luck!