The forest is beautiful, and Jimmy wants to take a different route everyday. He also wants to get home before dark, so he always takes a path to make progress towards his house. He considers taking a path from A to B to be progress if there exists a route from B to his home that is shorter than any possible route from A. Calculate how many different routes through the forest Jimmy might take.
InputInput contains several test cases followed by a line containing 0. Jimmy has numbered each intersection or joining of paths starting with 1. His office is numbered 1, and his house is numbered 2. The first line of each test case gives the number of intersections N, 1 < N ≤ 1000, and the number of paths M. The following M lines each contain a pair of intersections a b and an integer distance 1 ≤ d ≤ 1000000 indicating a path of length d between intersection a and a different intersection b. Jimmy may walk a path any direction he chooses. There is at most one path between any pair of intersections.
OutputFor each test case, output a single integer indicating the number of different routes through the forest. You may assume that this number does not exceed 2147483647
Sample Input
5 6 1 3 2 1 4 2 3 4 3 1 5 12 4 2 34 5 2 24 7 8 1 3 1 1 4 1 3 7 1 7 4 1 7 5 1 6 7 1 5 2 1 6 2 1 0
Sample Output
2 4
代码：
#include<cstdio> #include<cstring> #include<iostream> #include<algorithm> #include<queue> #include<stack> #include<set> #include<map> #include<vector> #include<cmath> #define Inf 0x3f3f3f3f const int maxn=1e5+5; typedef long long ll; using namespace std; int n,m; vector<int>G[1005]; int Map[1005][1005]; int dis[1005]; int s[1005]; void init() { for(int t=1;t<=n;t++) { for(int j=1;j<=n;j++) { Map[t][j]=Inf; } } for(int t=1;t<=n;t++) { Map[t][t]=0; } for(int t=1;t<=n;t++) { G[t].clear(); } memset(s,0,sizeof(s)); } void Dijstra(int u) { for(int t=1;t<=n;t++) { dis[t]=Inf; } priority_queue<int,vector<int>,greater<int> >q; q.push(u); dis[u]=0; int now; while(!q.empty()) { now=q.top(); q.pop(); for(int t=0;t<G[now].size();t++) { if(Map[now][G[now][t]]+dis[now]<dis[G[now][t]]) { dis[G[now][t]]=Map[now][G[now][t]]+dis[now]; q.push(G[now][t]); } } } } int dfs(int now) { if(now == 2) return 1; if(s[now]) return s[now]; for(int i = 0; i < G[now].size(); i++) { if(dis[now] > dis[ G[now][i] ]) { s[now] += dfs(G[now][i]); } } return s[now]; } int main() { while(scanf("%d",&n)!=EOF) { if(n==0) { break; } scanf("%d",&m); int u,v,w; init(); for(int t=0;t<m;t++) { scanf("%d%d%d",&u,&v,&w); if(Map[u][v]>w||Map[v][u]>w) { Map[u][v]=w; Map[v][u]=w; G[u].push_back(v); G[v].push_back(u); } } Dijstra(2); printf("%d ",dfs(1)); } return 0; }