POJ3683 Falsita

Posted 2020-08-02 GFY

http://poj.org/problem?id=3683

思路:2-SAT，输出任意一组方案，O(m+n)

  1 #include<cstdio>
  2 #include<iostream>
  3 #include<cmath>
  4 #include<cstring>
  5 #include<algorithm>
  6 int first[2000005],next[2000005],tot,go[2000005];
  7 int First[2000005],Next[2000005],Tot,Go[2000005];
  8 int b[200005],a[200005],n,ru[200005],low[200005],dfn[200005];
  9 int op[2000005],belong[200005],instack[200005],vis[200005],st[200005],c[200005],col[200005],sz,num,top;
 10 int read(){
 11     int t=0,f=1;char ch=getchar();
 12     while (ch<‘0‘||ch>‘9‘){if (ch==‘-‘)f=-1;ch=getchar();}
 13     while (‘0‘<=ch&&ch<=‘9‘){t=t*10+ch-‘0‘;ch=getchar();}
 14     return t*f;
 15 }
 16 void insert(int x,int y){
 17     tot++;
 18     go[tot]=y;
 19     next[tot]=first[x];
 20     first[x]=tot;
 21 }
 22 void Insert(int x,int y){
 23     Tot++;
 24     Go[Tot]=y;
 25     Next[Tot]=First[x];
 26     First[x]=Tot;
 27 }
 28 bool jud(int x,int y){
 29     if (b[x]<=a[y]||a[x]>=b[y]) return 0;
 30     else return 1;
 31 }
 32 void build(){
 33     for (int i=1;i<=n;i++)
 34      for (int j=i+1;j<=n;j++){
 35         if (jud(i*2-1,j*2)){
 36             insert(i*2-1,j*2-1);
 37             insert(j*2,i*2);
 38         }
 39         if (jud(i*2-1,j*2-1)){
 40             insert(i*2-1,j*2);
 41             insert(j*2-1,i*2);
 42         }
 43         if (jud(i*2,j*2)){
 44             insert(i*2,j*2-1);
 45             insert(j*2,i*2-1);
 46         }
 47         if (jud(i*2,j*2-1)){
 48             insert(i*2,j*2);
 49             insert(j*2-1,i*2-1);
 50         }
 51      }
 52 }
 53 void init(){
 54     n=read();
 55     for (int i=1;i<=n;i++){
 56         a[i*2]=read();
 57         a[i*2]=a[i*2]*60+read();
 58         b[i*2-1]=read();
 59         b[i*2-1]=b[i*2-1]*60+read();
 60         int x=read();
 61         b[i*2]=a[i*2]+x;
 62         a[i*2-1]=b[i*2-1]-x;
 63     }
 64 }
 65 void tarjan(int x){
 66     low[x]=dfn[x]=++sz;
 67     instack[x]=vis[x]=1;st[++top]=x;
 68     for (int i=first[x];i;i=next[i]){
 69         int pur=go[i];
 70         if (!vis[pur]){
 71             tarjan(pur);
 72             low[x]=std::min(low[x],low[pur]);
 73         }else if (instack[pur]){
 74             low[x]=std::min(low[x],dfn[pur]);
 75         }
 76     }
 77     if (low[x]==dfn[x]){
 78         num++;
 79         while (st[top]!=x){
 80             instack[st[top]]=0;
 81             belong[st[top]]=num;
 82             top--;
 83         }
 84             instack[st[top]]=0;
 85             belong[st[top]]=num;
 86             top--;
 87     }
 88 }
 89 void Tarjan(){
 90     for (int i=1;i<=2*n;i++)
 91      if (!vis[i]) tarjan(i);
 92 }
 93 bool judge(){
 94     for (int i=1;i<=n;i++)
 95      if (belong[i*2]==belong[i*2-1]) {
 96             puts("NO");
 97             return 1;
 98      }
 99     puts("YES");
100     return 0; 
101 }
102 void dfs(int x){
103     if (col[x]) return ;col[x]=-1;
104     for (int i=First[x];i;i=Next[i]){
105         int pur=Go[i];
106         dfs(pur);
107     }
108 }
109 void topsort(){
110     int t=0;
111     for (int i=1;i<=num;i++)
112      if (!ru[i]) c[++t]=i;
113     while (t){
114         int now=c[t--];
115         if (col[now]) continue;col[now]=1;
116         dfs(op[now]);
117         for (int i=First[now];i;i=Next[i]){
118             int pur=Go[i];
119             ru[pur]--;
120             if (ru[pur]==0) c[++t]=pur;
121         }
122     } 
123 }
124 void rebuild(){
125     for (int i=1;i<=2*n;i++)
126      for (int j=first[i];j;j=next[j]){
127             int pur=go[j];
128             if (belong[pur]==belong[i]) continue;
129             ru[belong[i]]++;
130             Insert(belong[pur],belong[i]);;
131      }
132     for (int i=1;i<=2*n;i++)
133      op[belong[i*2]]=belong[i*2-1],op[belong[i*2-1]]=belong[i*2];
134 }
135 void print(int x){
136     printf("%.2d:",x/60);
137     printf("%.2d ",x%60);
138 }
139 void Output(){
140     for (int i=1;i<=n;i++)
141      if (col[belong[i*2]]==1){
142             print(a[i*2]);print(b[i*2]);puts("");
143      }else{
144             print(a[i*2-1]);print(b[i*2-1]);puts("");    
145      }
146 }
147 int main(){
148     init();
149     build();
150     Tarjan();
151     if (judge()) return 0;
152     rebuild();
153     topsort();
154     Output();
155 }

为什么我会犯用错数组这种错误。。