poj3678Katu Puzzle

点为0或1，看满足m个条件时，是否有解

#include<iostream>
#include<map>
#include<string>
#include<cstring>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<queue>
#include<vector>
#include<algorithm>
using namespace std;
const int MAXN = 1010;
struct twosat
{
    int n,c;
    vector<int> g[MAXN<<1];
    bool mark[MAXN<<1];
    int s[MAXN<<1];    

    bool dfs(int x)
    {
        int i;
        if (mark[x^1])
            return 0;
        if (mark[x])
            return 1;
        mark[x] = 1;
        s[c++] = x;
        for (i = 0; i < g[x].size(); i++)
            if (!dfs(g[x][i]))
                return 0;
        return 1;
    }    

    void init(int n)
    {
        int i,t=n<<1;
        this->n = n;
        for (i = 0; i < t; i++)
            g[i].clear();
        memset(mark, 0, sizeof(mark));
    }    

    void add_clause(int x,int xval,int y,int yval)
    {
    	x=x*2+xval;
    	y=y*2+yval;
        g[x].push_back(y^1);
        g[y].push_back(x^1);
    }    

    bool solve()
    {
        int i,t=n<<1;
        for (i = 0; i < t; i += 2)
            if (!mark[i] && !mark[i + 1])
            {
                c = 0;
                if (!dfs(i))
                {
                    while (c > 0)
                        mark[s[--c]] =0;
                    if (!dfs(i + 1))
                        return 0;
                }
            }
        return 1;
    }
}ender;
int work(int a,int b,int k)
{
	return k==0?a&b:k==1?a|b:a^b;
}
int main()
{
	char s[100];
	int a,b,c,n,m,x,y,k;
	while(cin>>n>>m)
	{
		ender.init(n);
		while(m--)
		{
			scanf("%d%d%d%s",&a,&b,&c,s);
			k=strcmp(s,"AND")==0?0:strcmp(s,"OR")==0?1:2;
			for(x=0;x<2;x++)
				for(y=0;y<2;y++)
					if(work(x,y,k)!=c)
						ender.add_clause(a,x,b,y);
		}
		cout<<(ender.solve()?"YES":"NO")<<endl;

	}
	return 0;
}

Katu Puzzle

Description

Katu Puzzle is presented as a directed graph G(V, E) with each edge
e(a, b) labeled by a boolean operator op (one of AND, OR, XOR) and an integer
c (0 ≤ c ≤ 1). One Katu is solvable if one can find each vertex
V_i a value X_i (0 ≤ X_i ≤ 1) such that for each edge
e(a, b) labeled by op and c, the following formula holds:

X_a op X_b = c

The calculating rules are:

Given a Katu Puzzle, your task is to determine whether it is solvable.

Input

The first line contains two integers N (1 ≤ N ≤ 1000) and
M,(0 ≤ M ≤ 1,000,000) indicating the number of vertices and edges.

The following M lines contain three integers a (0 ≤ a <
N), b(0 ≤ b < N), c and an operator
op each, describing the edges.

Output

Output a line containing "YES" or "NO".

Sample Input

4 4
0 1 1 AND
1 2 1 OR
3 2 0 AND
3 0 0 XOR

Sample Output

YES

Hint

X₀ = 1, X₁ = 1,
X₂ = 0, X₃ = 1.

Source

POJ Founder Monthly Contest – 2008.07.27, Dagger