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  • HDU3062 Party (2-SAT)

    没注意边数T了N遍的我真是弱啊

    const int N = 2007;
    
    int n;
    
    struct Edge{
    	int nxt,pre;
    }e[1000007];
    int cntEdge,head[N];
    inline void add(int u,int v){
    	e[++cntEdge] = (Edge){head[u], v}, head[u] = cntEdge;
    }
    
    int dfn[N],dfnIndex,low[N],vis[N];
    int sta[N],top;
    int bcc[N],bccIndex;
    inline void Tarjan(int u){
    	dfn[u] = low[u] = ++dfnIndex;
    	vis[u] = true;
    	sta[++top] = u;
    	for(register int i = head[u]; i; i = e[i].nxt){
    		int v = e[i].pre;
    		if(!dfn[v]){
    			Tarjan(v);
    			low[u] = Min(low[u], low[v]);
    		}
    		else if(vis[v]){
    			low[u] = Min(low[u], dfn[v]);
    		}
    	}
    	if(dfn[u] == low[u]){
    		++bccIndex;
    		do{
    			bcc[sta[top]] = bccIndex;
    			vis[sta[top]] = false;
    		}while(sta[top--] != u);
    	}
    	
    }
    
    inline bool Judge(){
    	R(i,1,n){
    		if(bcc[i<<1] == bcc[i<<1|1])
    			return false;
    	}
    	return true;
    }
    int main(){
    	int m;
    	while(~scanf("%d%d", &n, &m)){
    		cntEdge = 0;
    		n <<= 1;
    		R(i,1,n){
    			head[i] = 0,
    			dfn[i] = 0,
    			low[i] = 0,
    			vis[i] = false;
    		}
    		n >>= 1;
    
    		R(i,1,m){
    			int a,b,c,d;
    			io >> a >> b >> c >> d;
    			a = (a<<1) + c;
    			b = (b<<1) + d;
    			add(a, b ^ 1);
    			add(b, a ^ 1);
    		}
    		
    		n <<= 1;
    		R(i,1,n){
    			if(!dfn[i])
    				Tarjan(i);
    		}
    		n >>= 1;
    		
    		if(Judge() == true)
    			printf("YES
    ");
    		else
    			printf("NO
    ");
    	}
    	return 0;
    }
    
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  • 原文地址:https://www.cnblogs.com/bingoyes/p/11177706.html
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