mirror of
https://github.com/This-weiyuqing/DSAndOS.git
synced 2026-10-17 18:55:44 +08:00
144 lines
3.1 KiB
C++
144 lines
3.1 KiB
C++
#include<stdio.h>
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#include<iostream>
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#include<string>
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#include<string.h>
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#include<algorithm>
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#include<iomanip>
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#include<vector>
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#include<time.h>
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#include<queue>
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#include<stack>
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#include<iterator>
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#include<math.h>
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#include<stdlib.h>
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#include<limits.h>
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#include<map>
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//#define ONLINE_JUDGE
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#define eps 1e-8
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#define INF 0x7fffffff
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#define FOR(i,a) for((i)=0;i<(a);(i)++)
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#define MEM(a) (memset((a),0,sizeof(a)))
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#define sfs(a) scanf("%s",a)
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#define sf(a) scanf("%d",&a)
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#define sfI(a) scanf("%I64d",&a)
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#define pf(a) printf("%d\n",a)
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#define pfI(a) printf("%I64d\n",a)
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#define pfs(a) printf("%s\n",a)
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#define sfd(a,b) scanf("%d%d",&a,&b)
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#define sft(a,b,c)scanf("%d%d%d",&a,&b,&c)
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#define for1(i,a,b) for(int i=(a);i<b;i++)
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#define for2(i,a,b) for(int i=(a);i<=b;i++)
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#define for3(i,a,b)for(int i=(b);i>=a;i--)
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#define MEM1(a) memset(a,0,sizeof(a))
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#define MEM2(a) memset(a,-1,sizeof(a))
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const double PI=acos(-1.0);
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template<class T> T gcd(T a,T b){return b?gcd(b,a%b):a;}
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template<class T> T lcm(T a,T b){return a/gcd(a,b)*b;}
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template<class T> inline T Min(T a,T b){return a<b?a:b;}
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template<class T> inline T Max(T a,T b){return a>b?a:b;}
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using namespace std;
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#define ll __int64
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int n,m;
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#define Mod 10
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#define N 10010
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#define M 1000010
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struct Edge{ //存储边的结构体
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int to;
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int next;
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};
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struct Node{ //存储点的结构体
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int id;
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int step;
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};
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struct sqQueue{ //队列的结构体
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Node *base;
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int front;
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int rear;
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};
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Edge edge[N]; //
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int head[N];
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int vis[N];
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int cnt;
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sqQueue Q;
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void Init(){
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memset(head,-1,sizeof head);
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cnt=0;
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}
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void addEdge(int u,int v){ //添加边
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edge[cnt].to = v;
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edge[cnt].next = head[u];
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head[u] = cnt++;
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}
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void InitQueue(sqQueue &Q){ //初始化队列
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Q.base = new Node[M];
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if(!Q.base)
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exit(OVERFLOW);
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Q.front = Q.rear = 0;
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return;
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}
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int QueueLength(sqQueue Q){ //求队列的长度
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return(Q.rear-Q.front+M)%M;
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}
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int EnQueue(sqQueue &Q,Node e){ //入队
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if((Q.rear+1)%M == Q.front)
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return 0;
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Q.base[Q.rear] = e;
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Q.rear = (Q.rear+1)%M;
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return 1;
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}
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int DeQueue(sqQueue &Q){ //出队
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if(Q.front == Q.rear)
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return 0;
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Q.front = (Q.front+1)%M;
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return 1;
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}
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Node getHead(sqQueue Q){ //得到队列头部的元素
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return Q.base[Q.front];
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}
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void bfs(){ //用bfs来搜索与初始点距离不超过7的点的个数占总数的百分比
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memset(vis,0,sizeof vis);
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InitQueue(Q);
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Node cur,next;
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cur.id = 0;
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cur.step = 0;
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EnQueue(Q,cur);
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vis[0] = 1;
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int num = 0;
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while(QueueLength(Q)){
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cur = getHead(Q);
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DeQueue(Q);
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if(cur.step>7){
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break;
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}
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num++;
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int s = cur.id;
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for(int p = head[s];p!=-1;p=edge[p].next){
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int v = edge[p].to;
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if(!vis[v]){
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next.id = v;
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next.step = cur.step + 1;
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vis[v] = 1;
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EnQueue(Q,next);
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}
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}
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}
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printf("%.4f\n",num*1.0/n);
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}
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int main(){
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#ifndef ONLINE_JUDGE
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freopen("in.txt","r",stdin);
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// freopen("out.txt","w",stdout);
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#endif
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while(sfd(n,m)!=EOF){ //n为顶点的数量，m为边的数量,点的编号从0-n-1
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Init(); //初始化
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int u,v;
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for(int i=0;i<m;i++){
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scanf("%d%d",&u,&v); //输入两个相邻的点
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addEdge(u,v);
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addEdge(v,u); //无向边
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}
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bfs();
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}
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return 0;
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}
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