Age of Moyu （2018 Multi-University Training Contest 7）

题目链接

 #include <bits/stdc++.h>
 using namespace std;
 typedef long long ll;
 inline ll read(){
     int x=,f=;char ch=getchar();
     while(ch>''||ch<''){if(ch=='-')f=-;ch=getchar();}
     while(ch>=''&&ch<=''){x=x*+ch-'';ch=getchar();}
     return x*f;
 }
 
 /***********************************************************/
 
 const int maxn = ;
 int n, m;
 int dis[maxn], head[maxn], look[maxn];
 queue<int>q;
 int ans, cas;
 
 struct Edge
 {
     int u, v, w, next, vis;
 }edge[maxn*];
 
 void add_edge(int u, int v, int w){
     edge[cas].u = u; edge[cas].v = v; edge[cas].w = w;
     edge[cas].next = head[u]; edge[cas].vis = ;
     head[u] = cas++;
 }
 
 void dfs(int rt, int cl, int num){
     if(rt == n) {
         ans = num;
         return;
     }
     if(!look[rt]){
         look[rt] = ;
         dis[rt] = num;
         q.push(rt);
     }
     for(int i = head[rt];i != -;i = edge[i].next){
         if(edge[i].vis) continue;
         if(edge[i].w == cl){
             edge[i].vis = ;
             dfs(edge[i].v, cl, num);
         }
     }
     return;
 }
 
 int bfs(){
     while(!q.empty()) q.pop();
     q.push();            //从一开始走
     dis[] = ;
     look[] = ;
     while(!q.empty()){
         int now = q.front(); q.pop();
         for(int i = head[now];i != -;i = edge[i].next){
             if(edge[i].vis) continue;    //每条边只走一次
             int v = edge[i].v;
             edge[i].vis = ;
             dfs(v, edge[i].w, dis[now]+);    //把所有与当前路径相同权值的路径加入
             if(ans > ) break;
         }
         if(ans > ) break;
     }
     return ans;
 }
 
 void init(){
     cas = ;
     memset(head, -, sizeof(head));
     memset(look, , sizeof(look));
     memset(dis, 0x7f, sizeof(dis));
 }
 
 int main(){
     while(~scanf("%d%d", &n, &m)){
         init();
         for(int i = ;i <= m;i++){
             int u, v, w;
             u = read(); v = read(); w = read();
             add_edge(u, v, w);
             add_edge(v, u, w);
         }
         ans = -;
         ans = bfs();
         printf("%d\n", ans);
     }
     return ;
 }