• HDU-4607 Park Visit bfs | DP | dfs


      题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=4607

      首先考虑找一条最长链长度k,如果m<=k+1,那么答案就是m。如果m>k+1,那么最长链上还有其他分支,来回走一遍,因此答案为2*m-k-1。。。求最长链可以DP,两次BFS或者DFS等。。

      1 //STATUS:C++_AC_453MS_3524KB
      2 #include <functional>
      3 #include <algorithm>
      4 #include <iostream>
      5 //#include <ext/rope>
      6 #include <fstream>
      7 #include <sstream>
      8 #include <iomanip>
      9 #include <numeric>
     10 #include <cstring>
     11 #include <cassert>
     12 #include <cstdio>
     13 #include <string>
     14 #include <vector>
     15 #include <bitset>
     16 #include <queue>
     17 #include <stack>
     18 #include <cmath>
     19 #include <ctime>
     20 #include <list>
     21 #include <set>
     22 #include <map>
     23 using namespace std;
     24 //using namespace __gnu_cxx;
     25 //define
     26 #define pii pair<int,int>
     27 #define mem(a,b) memset(a,b,sizeof(a))
     28 #define lson l,mid,rt<<1
     29 #define rson mid+1,r,rt<<1|1
     30 #define PI acos(-1.0)
     31 //typedef
     32 typedef __int64 LL;
     33 typedef unsigned __int64 ULL;
     34 //const
     35 const int N=100010;
     36 const LL INF=0x3f3f3f3f;
     37 const int MOD=1000000007,STA=8000010;
     38 const LL LNF=1LL<<60;
     39 const double EPS=1e-8;
     40 const double OO=1e15;
     41 const int dx[4]={-1,0,1,0};
     42 const int dy[4]={0,1,0,-1};
     43 const int day[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
     44 //Daily Use ...
     45 inline int sign(double x){return (x>EPS)-(x<-EPS);}
     46 template<class T> T gcd(T a,T b){return b?gcd(b,a%b):a;}
     47 template<class T> T lcm(T a,T b){return a/gcd(a,b)*b;}
     48 template<class T> inline T lcm(T a,T b,T d){return a/d*b;}
     49 template<class T> inline T Min(T a,T b){return a<b?a:b;}
     50 template<class T> inline T Max(T a,T b){return a>b?a:b;}
     51 template<class T> inline T Min(T a,T b,T c){return min(min(a, b),c);}
     52 template<class T> inline T Max(T a,T b,T c){return max(max(a, b),c);}
     53 template<class T> inline T Min(T a,T b,T c,T d){return min(min(a, b),min(c,d));}
     54 template<class T> inline T Max(T a,T b,T c,T d){return max(max(a, b),max(c,d));}
     55 //End
     56 
     57 struct Edge{
     58     int u,v;
     59 }e[N*2];
     60 int first[N],next[N*2],d[N];
     61 int Ca,T,n,m,mt;
     62 
     63 void adde(int a,int b)
     64 {
     65     e[mt].u=a;e[mt].v=b;
     66     next[mt]=first[a];first[a]=mt++;
     67     e[mt].u=b;e[mt].v=a;
     68     next[mt]=first[b];first[b]=mt++;
     69 }
     70 
     71 int bfs(int s)
     72 {
     73     int u,i,hig;
     74     mem(d,0);
     75     d[s]=1;
     76     queue<int> q;
     77     q.push(s);
     78     hig=-1;
     79     while(!q.empty())
     80     {
     81         u=q.front();q.pop();
     82         for(i=first[u];i!=-1;i=next[i]){
     83             if(!d[e[i].v]){
     84                 d[e[i].v]=d[e[i].u]+1;
     85                 if(d[e[i].v]>hig){
     86                     hig=d[e[i].v];
     87                     T=e[i].v;
     88                 }
     89                 q.push(e[i].v);
     90             }
     91         }
     92     }
     93     return hig;
     94 }
     95 
     96 int main()
     97 {
     98  //   freopen("in.txt","r",stdin);
     99     int i,j,a,b,hig;
    100     scanf("%d",&Ca);
    101     while(Ca--)
    102     {
    103         scanf("%d%d",&n,&m);
    104         mem(first,-1);mt=0;
    105         for(i=1;i<n;i++){
    106             scanf("%d%d",&a,&b);
    107             adde(a,b);
    108         }
    109         bfs(1);
    110         hig=bfs(T);
    111 
    112         while(m--){
    113             scanf("%d",&a);
    114             if(a>hig){
    115                 printf("%d
    ",2*a-hig-1);
    116             }
    117             else printf("%d
    ",a-1);
    118         }
    119     }
    120     return 0;
    121 }
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  • 原文地址:https://www.cnblogs.com/zhsl/p/3209565.html
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