The Preliminary Contest for ICPC Asia Nanjing 2019 H. Holy Grail

题目链接：https://nanti.jisuanke.com/t/41305

题目说的很明白。。。只需要反向跑spfa然后输入-dis，然后添-dis的一条边就好了。。。

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  1 #include <iostream>
  2 #include <cstdio>
  3 #include <cstring>
  4 #include <algorithm>
  5 #include <queue>
  6 #include <map>
  7 #include <cmath>
  8 #include <iomanip>
  9 using namespace std;
 10 
 11 typedef long long LL;
 12 #define inf 1e14
 13 #define rep(i, j, k) for (int i = (j); i <= (k); i++)
 14 #define rep__(i, j, k) for (int i = (j); i < (k); i++)
 15 #define per(i, j, k) for (int i = (j); i >= (k); i--)
 16 #define per__(i, j, k) for (int i = (j); i > (k); i--)
 17 
 18 const int N = 310;
 19 int head[N];
 20 int cnt;
 21 bool vis[N];
 22 LL dis[N];
 23 queue<int > que;
 24 int n,m;
 25 
 26 struct Edge{
 27     int to;
 28     LL w;
 29     int next;
 30 }e[510];
 31 
 32 void add(int u,int v,LL w){
 33     e[cnt].to = v;
 34     e[cnt].w = w;
 35     e[cnt].next = head[u];
 36     head[u] = cnt++;
 37 }
 38 
 39 void spfa(int s){
 40 
 41     while(!que.empty()) que.pop();
 42     rep__(i,0,n){
 43         vis[i] = false;
 44         dis[i] = inf;
 45     }
 46 
 47     dis[s] = 0;
 48     que.push(s);
 49 
 50     int u,v;
 51     LL w;
 52     while(!que.empty()){
 53         u = que.front();
 54  //       cout << "u " << u << endl;
 55         que.pop();
 56         vis[u] = false;
 57         for(int o = head[u]; ~o; o = e[o].next){
 58             v = e[o].to;
 59             w = e[o].w;
 60             if(dis[v] > dis[u] + w){
 61                 dis[v] = dis[u] + w;
 62                 if(!vis[v]){
 63                     vis[v] = true;
 64                     que.push(v);
 65                 }
 66             }
 67         }
 68     }
 69 }
 70 
 71 int main(){
 72 
 73     int T;
 74     scanf("%d",&T);
 75 
 76     int u,v;
 77     LL w;
 78     rep(o,1,T){
 79         scanf("%d%d",&n,&m);
 80 
 81         rep__(i,0,n) head[i] = -1;
 82         cnt = 0;
 83 
 84         rep(i,1,m){
 85             scanf("%d%d%lld",&u,&v,&w);
 86             add(u,v,w);
 87         }
 88 
 89         // rep__(i,o,n){
 90         //     cout << " u " << i << endl;
 91 
 92         //     for(int  o = head[i]; ~o; o = e[o].next){
 93         //         cout << e[o].to << " " << e[o].w << endl;
 94         //     }
 95         // }
 96 
 97         rep(i,1,6){
 98             scanf("%d%d",&u,&v);
 99             spfa(v);
100             printf("%lld\n",-dis[u]);
101             add(u,v,-dis[u]);
102         }
103     }
104 
105     getchar();getchar();
106     return 0;
107 }