Noi roll cu after July oi life

7-24

A bzoj1001, Tun a long time problem, has not written, write quite smooth, did so long Bzoj, did not put it a off

Network flow, plane map to dual diagram, and then run the shortest way, similar proof seems like the maximum flow minimum cut theorem, the maximum conversion to the minimum, specifically do not know Qaq

Look at the bzoj1064, think of may be the size of the ring GCD,LCM, and then found a lot of details, simply do not find a simple ring. Then decisive to search the puzzle, tangled up for a while, and then found a new technique, immediately before the bright, but this technique seems to be not widely used.

For each side x->y, we build x->y side, edge right 1, build y->x side, edge right 1, and then DFS again, to each point designator, when DFS to the repetition point, the size of this ring is the original number and now should be the number of the absolute value of the difference, This method is applicable because there are two different paths between two points for this ring between two points (not the same ring).

Then saw bzoj1052, as if casually violent violence passed.

There must be an L-shaped box at the corner of the outermost rectangular box, and then recursive on the line, for each case, I only need the current one solution, and then recursive to find a solution, this idea is very good.

and went to see the bzoj2753, a start to see the wrong problem ~\ (≧▽≦)/~. The first question is very clear, the second one does not look. Look at the puzzle of the smallest tree in a few words, and go to see, the more the more will not, and found that as if why and check set also some links, and tangled, tangled a good while, finally understand.

Algorithm to see the solution, assuming this algorithm is not, then it will not be selected, but the choice of this side of the answer is not likely to be bad, because it is still in, should not be worse than it, it seems that the algorithm can sometimes be used to each other, it is the special nature of the problem, seemingly impossible things, but also possible side, Seize the nature of each algorithm. such as Kruskal, its practical significance is to join this side is no better than not to add this side difference, then this edge is can add, this can into into the greedy idea, very good.

(not to be continued)

Noi roll cu after July oi life