East Central North America Region 2015
E
每过一秒，当前点会把它的值传递给所有相邻点，问t时刻该图的值
1 #include <iostream> 2 #include <cstdio> 3 #include <algorithm> 4 #include <list> 5 #include <map> 6 #include <stack> 7 #include <vector> 8 #include <cstring> 9 #include <sstream> 10 #include <string> 11 #include <cmath> 12 #include <queue> 13 using namespace std; 14 #define clc(a,b) memset(a,b,sizeof(a)) 15 #define inf 0x3f3f3f3f 16 const int N=10010; 17 const int MOD = 1e9+7; 18 #define LL long long 19 20 void fre() { 21 freopen("in.txt","r",stdin); 22 } 23 inline int r() { 24 int x=0,f=1;char ch=getchar(); 25 while(ch>'9'||ch<'0') {if(ch=='-') f=-1;ch=getchar();} 26 while(ch>='0'&&ch<='9') { x=x*10+ch-'0';ch=getchar();}return x*f; 27 } 28 29 vector<int>g[101]; 30 LL countt[110]; 31 LL val[110]={0}; 32 33 int main(){ 34 int n,m,s,t; 35 n=r(); 36 m=r(); 37 s=r(); 38 t=r(); 39 for(int i=0;i<=n;i++) 40 g[i].clear(); 41 for(int i=0;i<m;i++){ 42 int x,y; 43 x=r(); 44 y=r(); 45 g[x].push_back(y); 46 g[y].push_back(x); 47 } 48 val[s]=1; 49 for(int i=1;i<=t;i++){ 50 for(int j=0;j<n;j++) 51 countt[j]=0; 52 for(int j=0;j<n;j++){ 53 LL num=val[j]; 54 for(int p=0;p<(int)g[j].size();p++){ 55 int v=g[j][p]; 56 countt[v]+=num; 57 } 58 } 59 for(int j=0;j<n;j++){ 60 val[j]=countt[j]; 61 } 62 } 63 LL ans=0; 64 for(int i=0;i<n;i++) 65 ans+=val[i]; 66 printf("%lld\n",ans); 67 return 0; 68 }
