Description
SAT was the first known NP-complete problem. The problem remains NP-complete even if all expressions are written in conjunctive normal form with 3 variables per clause (3-CNF), yielding the 3-SAT problem. A K-SATproblem can be described as follows:
There are n persons, and m objects. Each person makes K wishes, for each of these wishes either he wants to take an object or he wants to reject an object. You have to take a subset of the objects such that every person is happy. A person is happy if at least one of his K wishes is kept. For example, there are 3 persons, 4 objects, and K = 2, and
Person 1 says, "take object 1 or reject 2."
Person 2 says, "take object 3 or 4."
Person 3 says, "reject object 3 or 1."
So, if we take object 1 2 3, then it is not a valid solution, since person 3 becomes unhappy. But if we take 1 2 4 then everyone becomes happy. If we take only 4, it's also a valid solution. Now you are given the information about the persons' wishes and the solution we are currently thinking. You have to say whether the solution is correct or not.
Input
Input starts with an integer T (≤ 100), denoting the number of test cases.
Each case starts with a line containing three integers n, m, K (1 ≤ n, m, K ≤ 30). Each of the next nlines contains K space separated integers where the ith line denotes the wishes of the ith person. Each of the integers in a line will be either positive or negative. Positive means the person wants the object in the solution; negative means the person doesn't want that in the solution. You can assume that the absolute value of each of the integers will lie between 1 and m.
The next line contains an integer p (0 ≤ p ≤ m) denoting the number of integers in the solution, followed byp space separated integers each between 1 and m, denoting the solution. That means the objects we have taken as solution set.
Output
For each case, print the case number and 'Yes' if the solution is valid or 'No' otherwise.
Sample Input
2
3 4 2
+1 -2
+3 +4
-3 -1
1 4
1 5 3
+1 -2 +4
2 2 5
Sample Output
Case 1: Yes
Case 2: No
题解：n个人找对象，对象从1--m，负数代表不要，正数代表要；现在给一组数，问是否满足所有人的意愿；
代码：
#include<cstdio> #include<cstring> #include<algorithm> #include<set> using namespace std; int mp[50][50]; int vis[1010]; int p; int n, m, k; set<int>st; bool js(){ for(int i = 1; i <= n; i++){ int flot = 0; for(int j = 1; j <= k; j++){ if(st.count(mp[i][j])){ flot = 1; break; } } if(!flot)return false; } return true; } int main(){ int T, kase = 0; scanf("%d", &T); while(T--){ scanf("%d%d%d", &n, &m, &k); for(int i = 1; i <= n; i++){ for(int j = 1; j <= k; j++){ scanf("%d", &mp[i][j]); } } scanf("%d", &p); st.clear(); memset(vis, 0, sizeof(vis)); int x; for(int i = 1; i <= p; i++){ scanf("%d", &x); st.insert(x); vis[x] = 1; } for(int i = 1; i<= m; i++){ if(!vis[i])st.insert(-i); } if(js())printf("Case %d: Yes ", ++kase); else printf("Case %d: No ", ++kase); } return 0; }