简单搜索技巧和剪枝

2531Network SaboteurTime Limit: 2000MS Memory Limit: 65536KTotal Submissions: 7274 Accepted: 3199 DescriptionA university network is composed of N computers. System administrators gathered information on the traffic between nodes, and carefully divided the network into two subnetworks in order to minimize traffic between parts.A disgruntled computer science student Vasya, after being expelled from the university, decided to have his revenge. He hacked into the university network and decided to reassign computers to maximize the traffic between two subnetworks. Unfortunately, he found that calculating such worst subdivision is one of those problems he, being a student, failed to solve. So he asks you, a more successful CS student, to help him.The traffic data are given in the form of matrix C, where Cij is the amount of data sent between ith and jth nodes (Cij = Cji, Cii = 0). The goal is to divide the network nodes into the two disjointed subsets A and B so as to maximize the sum ∑Cij (i∈A,j∈B).InputThe first line of input contains a number of nodes N (2 <= N <= 20). The following N lines, containing N space-separated integers each, represent the traffic matrix C (0 <= Cij <= 10000).Output file must contain a single integer -- the maximum traffic between the subnetworks.OutputOutput must contain a single integer -- the maximum traffic between the subnetworks.Sample Input30 50 3050 0 4030 40 0Sample Output90SourceNortheastern Europe 2002, Far-Eastern Subregion1416Shredding CompanyTime Limit: 1000MS Memory Limit: 10000KTotal Submissions: 2882 Accepted: 1644 DescriptionYou have just been put in charge of developing a new shredder for the Shredding Company Although a "normal" shredder would just shred sheets of paper into little pieces so that the contents would become unreadable, this new shredder needs to have the following unusual basic characteristics.1.The shredder takes as input a target number and a sheet of paper with a number written on it.2.It shreds (or cuts) the sheet into pieces each of which has one or more digits on it.3.The sum of the numbers written on each piece is the closest possible number to the target number, without going over it.For example, suppose that the target number is 50, and the sheet of paper has the number 12346. The shredder would cut the sheet into four pieces, where one piece has 1, another has 2, the third has 34, and the fourth has 6. This is because their sum 43 (= 1 + 2 + 34 + 6) is closest to the target number 50 of all possible combinations without going over 50. For example, a combination where the pieces are 1, 23, 4, and 6 is not valid, because the sum of this combination 34 (= 1 + 23 + 4 + 6) is less than the above combination's 43. The combination of 12, 34, and 6 is not valid either, because the sum 52 (= 12 + 34 + 6) is greater than the target number of 50.Figure 1. Shredding a sheet of paper having the number 12346 when the targetnumber is 50There are also three special rules :1.If the target number is the same as the number on the sheet of paper, then the paper is not cut.For example, if the target number is 100 and the number on the sheet of paper is also 100, thenthe paper is not cut.2.If it is not possible to make any combination whose sum is less than or equal to the target number, then error is printed on a display. For example, if the target number is 1 and the number on the sheet of paper is 123, it is not possible to make any valid combination, as the combination with the smallest possible sum is 1, 2,3. The sum for this combination is 6, which is greater than the target number, and thus error is printed.3.If there is more than one possible combination where the sum is closest to the target number without going over it, then rejected is printed on a display. For example, if the target number is 15, and the number on the sheet of paper is 111, then there are two possible combinations with the highest possible sum of 12: (a) 1 and 11 and (b) 11 and 1; thus rejected is printed. In order to develop such a shredder, you have decided to first make a simple program that would simulate the above characteristics and rules. Given two numbers, where the first is the target number and the second is the numberon the sheet of paper to be shredded, you need to figure out how the shredder should "cut up" the second number.InputThe input consists of several test cases, each on one line, as follows :tl num1t2 num2...tn numn0 0Each test case consists of the following two positive integers, which are separated by one space : (1) the first integer (ti above) is the target number, (2) the second integer (numi above) is the number that is on the paper to be shredded.Neither integers may have a 0 as the first digit, e.g., 123 is allowed but 0123 is not. You may assume that both integers are at most 6 digits in length. A line consisting of two zeros signals the end of the input.OutputFor each test case in the input, the corresponding output takes one of the following three types :sum part1 part2 ...rejectederrorIn the first type, partj and sum have the following meaning :1.Each partj is a number on one piece of shredded paper. The order of partj corresponds to the order of the original digits on the sheet of paper.2.sum is the sum of the numbers after being shredded, i.e., sum = part1 + part2 +... Each number should be separated by one space.The message error is printed if it is not possible to make any combination, and rejected if there ismore than one possible combination.No extra characters including spaces are allowed at the beginning of each line, nor at the end of each line.Sample Input50 12346376 144139927438 92743818 33129 314225 1299111 33333103 8621506 11040 0Sample Output43 1 2 34 6283 144 139927438 92743818 3 3 12error21 1 2 9 9rejected103 86 2 15 0rejectedSourceJapan 2002 Kanazawa2676SudokuTime Limit: 2000MS Memory Limit: 65536KTotal Submissions: 10181 Accepted: 5081 Special Judge DescriptionSudoku is a very simple task. A square table with 9 rows and 9 columns is divided to 9 smaller squares 3x3 as shown on the Figure. In some of the cells are written decimal digits from 1 to 9. The other cells are empty. The goal is to fill the empty cells with decimal digits from 1 to 9, one digit per cell, in such way that in each row, in each column and in each marked 3x3 subsquare, all the digits from 1 to 9 to appear. Writea program to solve a given Sudoku-task.InputThe input data will start with the number of the test cases. For each test case, 9 lines follow, corresponding to the rows of the table. On each line a string of exactly 9 decimal digits is given, corresponding to the cells in this line. If a cell is empty it is represented by 0.OutputFor each test case your program should print the solution in the same format as the input data. The empty cells have to be filled according to the rules. If solutions is not unique, then the program may print any one of them.Sample Input1103000509002109400000704000300502006060000050700803004000401000009205800804000107Sample Output143628579572139468986754231391542786468917352725863914237481695619275843854396127SourceSoutheastern Europe 20051129Channel AllocationTime Limit: 1000MS Memory Limit: 10000KTotal Submissions: 9638 Accepted: 4904 DescriptionWhen a radio station is broadcasting over a very large area, repeaters are used to retransmit the signal so that every receiver has a strong signal. However, the channels used by each repeater must be carefully chosen so that nearby repeaters do not interfere with one another. This condition is satisfied if adjacent repeaters use different channels.Since the radio frequency spectrum is a precious resource, the number of channels required by a given network of repeaters should be minimised. You have to write a program that reads in a description of a repeater network and determines the minimum number of channels required.InputThe input consists of a number of maps of repeater networks. Each map begins with a line containing the number of repeaters. This is between 1 and 26, and the repeaters are referred to by consecutive upper-case letters of the alphabet starting with A. For example, ten repeaters would have the names A,B,C,...,I and J. A network with zero repeaters indicates the end of input.Following the number of repeaters is a list of adjacency relationships. Each line has the form:A:BCDHwhich indicates that the repeaters B, C, D and H are adjacent to the repeater A. The first line describes those adjacent to repeater A, the second those adjacent to B, and so on for all of the repeaters. If a repeater is not adjacent to any other, its line has the formA:The repeaters are listed in alphabetical order.Note that the adjacency is a symmetric relationship; if A is adjacent to B, then B is necessarily adjacent to A. Also, since the repeaters lie in a plane, the graph formed by connecting adjacent repeaters does not have any line segments that cross.OutputFor each map (except the final one with no repeaters), print a line containing the minumum number of channels needed so that no adjacent channels interfere. The sample output shows the format of this line. Take care that channels is in the singular form when only one channel is required.Sample Input2A:B:4A:BCB:ACDC:ABDD:BC4A:BCDB:ACDC:ABDD:ABCSample Output1 channel needed.3 channels needed.4 channels needed. SourceSouthern African 2001。