HDU 1054 最小顶点覆盖

http://acm.hdu.edu.cn/showproblem.php?pid=1054

#include<iostream>#include<cstdio>#include<cstring>#include<cmath>using namespace std;#define N 1501bool h[N];int pre[N];int n;int head[N];struct Node{int v,next;Node(){};Node(int a,int b):next(a),v(b){};}E[N*N];int NE;void insert(int u,int v){E[NE]=Node(head[u],v);head[u]=NE++;}bool dfs(int u){for(int i=head[u];i!=-1;i=E[i].next){int v=E[i].v;if(!h[v]){h[v]=1;if(pre[v]==-1||dfs(pre[v])){pre[v]=u;return true;}}}return false;}int atoi(char *p){int len=strlen(p);int ans=0;for(int i=0;i<len;i++)ans+=(p[i]-'0')*(int)pow(10.0,len-i-1);return ans;}int f(char *ch){int len=strlen(ch),k=0;char p[20];for(int i=0;i<len;i++)if(ch[i]=='('){for(int j=i+1;j<len-1;j++)p[k++]=ch[j];p[k]='/0';return atoi(p);}return 0;}int ff(char *p){int len=strlen(p),k=0;;char ch[20];for(int i=0;i<len;i++){if(p[i]==':')break;ch[k++]=p[i];}ch[k]='/0';return atoi(ch);}int main(void){while(~scanf("%d",&n)){NE=0;memset(head,-1,sizeof(head));for(int i=0;i<n;i++){char ch[20];scanf("%s",ch);int k=ff(ch);int temp=f(ch);while(temp--){int y;scanf("%d",&y);insert(k,y);insert(y,k);}}memset(pre,-1,sizeof(pre));int ans=0;for(int i=0;i<n;i++){memset(h,0,sizeof(h));if(dfs(i))ans++;}printf("%d/n",ans/2);}} 

用邻接表存，不然会超时！