M × N Puzzle Time Limit: 4000MS   Memory Limit: 131072K Total Submissions: 4860   Accepted: 1321 Description The Eight Puzzle, among other sliding-tile puzzles, is one of the famous problems in artificial intelligence. Along with chess, tic-tac-toe a…

id=2983">[POJ 2983]Is the Information Reliable? (差分约束系统) Is the Information Reliable? Time Limit: 3000MS   Memory Limit: 131072K Total Submissions: 12244   Accepted: 3861 Description The galaxy war between the Empire Draco and the Commonwealth of…

http://poj.org/problem?id=2983 题意:N 个 defense stations,M条消息,消息有精确和模糊之分,若前边为P.则为精确消息,有两个defense stations和他们之间的距离,若为P A B X 则是精确消息,并且A在B北边X光年远,V A B则是模糊消息,A在B北边,不知道距离,但至少是1光年远. 思路 :这个题要转化成差分约束.因为dist[a]-dist[b] = x,所以转化成差分约束x<=dist[a]-dist[b]<=x ,模糊消息…

题链: http://poj.org/problem?id=2983 题解: 差分约束. 1).对于条件(P u v w),不难发现反映到图上就是: $dis[u]-dis[v]=w$,所以添加两条边: u → v : -w v → u : w 2).对于条件(V,u,v),反映到图上即为: $dis[u]-dis[v]>=1$,所以添加一条边: v → u : 1 建好图后,dfs版spfa判一下是否存在正环就好了. (出现正环代表Unreliable,否则就是Reliable) 代码: #i…

http://poj.org/problem?id=2983 题目大意: 星际大战开始了.你购买了情报,需要判断它的准确性.已知地方的根据地在由南向北排成一条直线.P A B X,表示A在B北面距离X光年的地方,另一种是V A B,表示只知道A在B的北面至少1光年的地方. 思路: 可转化为差分约束. 对于P A B X来说因为A-B=X (因为他们相距X光年,我们取北边为正方向) 可以记做:  A-B >=X &&  A-B<=X,即A-B>=X && B…

http://poj.org/problem?id=3678 题意:很幼稚的题目直接看英文题面= = #include <cstdio> #include <cstring> #include <algorithm> #include <cmath> #include <iostream> using namespace std; const int N=1000*2+10, M=N*N*4; struct E { int next, to; }…

                                                           M × N Puzzle Time Limit: 4000MS   Memory Limit: 131072K Total Submissions: 4112   Accepted: 1140 Description The Eight Puzzle, among other sliding-tile puzzles, is one of the famous problems…

http://poj.org/problem?id=1651 题意:给出n个数字,每取中间一个数,就会使得权值加上中间这个数和两边的乘积,求取剩两个数最少的权值是多少. 思路:区间dp. 一开始想了挺久还是写不出方程,做了点别的事回来再想就突然觉得很简单了. 一开始使得长度为1和2的区间dp[i][j]为0. 然后dp[i][j] = min(dp[i][k] + dp[k][j] + w[k] * w[i] * w[j]). 枚举的k为中间拿掉的数,然后和左右的区间和相加就是最后答案了. #i…

Multiplication Puzzle Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 7118   Accepted: 4385 Description The multiplication puzzle is played with a row of cards, each containing a single positive integer. During the move player takes one…

裸差分约束. //#pragma comment(linker, "/STACK:1024000000,1024000000") #include<cstdio> #include<cstring> #include<cstdlib> #include<algorithm> #include<iostream> #include<sstream> #include<cmath> #include<…