【HDU4430】【ZOJ3656】Bit Magic 2-SAT

2-SAT模版题
使用位运算之间的依赖关系建图。
需要注意的是
x | y = 0 时
x -> !x, y->!y

x&1 = 1时候
!x -> x, !y->y

直接把所有位放在一起判断的话内存不够，所以每一位判断一次。
要注意数组从零开始。
同时在ＺＯＪ上要注意判断对角线上是不是都是０。

#include<bits/stdc++.h>using namespace std;const int maxn = 2010;int head[maxn],tot;struct edge{    int to,next;}e[1000010];void addedge(int u,int v){    e[tot].to = v;    e[tot].next = head[u];    head[u] = tot++;}int b[510][510];int dfn[maxn],low[maxn],stk[maxn],belong[maxn],top,ins[maxn],clk,scc;int num[maxn];int N;void init(){    memset(head,-1,sizeof(head));    memset(dfn,0,sizeof(dfn));    memset(low,0,sizeof(low));    memset(ins,0,sizeof(ins));    tot = top = clk = scc = 0;}void Tarjan(int u){    int v;    dfn[u] = low[u] = ++clk;    stk[top++] = u;    ins[u] = 1;    for(int i = head[u];i!=-1;i=e[i].next){        // if(!conn[u][v]) continue;        int v = e[i].to;        if(!dfn[v]){            Tarjan(v);            low[u] = min(low[u],low[v]);        }else if(ins[v]){            low[u] = min(low[u],dfn[v]);        }    }    if(low[u] == dfn[u]){        scc++;        do{            v = stk[--top];            ins[v] = 0;            belong[v] = scc;            num[scc]++;        }while(u != v);    }}int main(){    // freopen("a.in","r",stdin);    int n;    while(~scanf("%d",&n)){        int t;        bool flag = 0;        N = 2 * n;        for(int i = 0;i<n;i++){            for(int j = 0;j<n;j++){                scanf("%d",&b[i][j]);            }        }        for(int k = 0;k<32;k++){            init();            for(int i = 0;i<n;i++){                for(int j = 0;j<n;j++){                    if(i == j){                        if(b[i][i] != 0)                            flag = 1;                        continue;                    }                    if(i%2 == 1 && j%2 == 1){                        if(b[i][j] & (1<<k)){                            addedge(i,j+n);                            addedge(j,i+n);                        }else{                            addedge(i+n,i);                            addedge(j+n,j);                                                    }                    }else if(i%2 == 0 && j%2 == 0){                        if(b[i][j] & (1<<k)){                            addedge(i,i+n);                            addedge(j,j+n);                        }else{                            addedge(i+n,j);                            addedge(j+n,i);                                       }                    }else{                        if(b[i][j] & (1<<k)){                            addedge(i,j+n);                            addedge(j,i+n);                            addedge(i+n,j);                            addedge(j+n,i);                        }else{                            addedge(i,j);                            addedge(j,i);                            addedge(i+n,j+n);                            addedge(j+n,i+n);;                                                    }                    }                }            }            if(flag)                break;            for(int i = 0;i<N;i++)                if(!dfn[i])                    Tarjan(i);            // for(int i = 0;i<N;i++){            //     cout<<belong[i]<<' ';            // }            // cout<<endl;            for(int i = 0;i<n;i++){                if(belong[i] == belong[i+n])                    flag = 1;            }        }        printf("%s\n",flag?"NO":"YES");    }}