P1462-通往奥格瑞玛的道路

  1 #include <bits/stdc++.h>
  2 #define pb push_back
  3 #define _for(i,a,b) for(int i = (a);i < (b);i ++)
  4 #define INF 1000000003
  5 #define ll long long
  6 
  7 using namespace std;
  8 
  9 const int maxn = 50003;
 10 inline ll read()
 11 {
 12     ll ans = 0;
 13     char ch = getchar(), last = ‘ ‘;
 14     while(!isdigit(ch)) last = ch, ch = getchar();
 15     while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - ‘0‘, ch = getchar();
 16     if(last == ‘-‘) ans = -ans;
 17     return ans;
 18 }
 19 inline void write(ll x)
 20 {
 21     if(x < 0) x = -x, putchar(‘-‘);
 22     if(x >= 10) write(x / 10);
 23     putchar(x % 10 + ‘0‘);
 24 }
 25 struct edge
 26 {
 27     ll to;
 28     ll cost;
 29 };
 30 vector<edge> G[maxn];
 31 
 32 ll V,E,B;
 33 
 34 typedef pair<ll,ll> P;//first 是最短距离，second 是顶点编号 
 35 ll d[maxn];
 36 ll f[maxn];
 37 
 38 bool shortest_path(ll s,ll lim)
 39 {
 40     priority_queue<P,vector<P>,greater<P>> que;
 41     ll ans = -1;
 42     _for(i,1,V+1)
 43         d[i] = INF;
 44     d[s] = 0;
 45     que.push(P{0,s});
 46 
 47     while(!que.empty())
 48     {
 49         P p = que.top();que.pop();
 50         ll v = p.second;
 51         if(d[v] < p.first) continue;
 52         _for(i,0,G[v].size())
 53         {
 54             edge e = G[v][i];
 55             if(d[e.to] > d[v] + e.cost && f[e.to] <= lim)
 56             {
 57                 d[e.to] = d[v] + e.cost;
 58                 que.push(P{d[e.to],e.to});
 59             }
 60         }
 61     }
 62     if(d[V]>=B)
 63         return false;
 64     return true;
 65 }
 66 bool C(ll dd)
 67 {
 68     return shortest_path(1,dd);
 69 }
 70 void solve()
 71 {
 72     ll t[maxn];
 73     memcpy(t,f,maxn*sizeof(ll));
 74     sort(t+1,t+V+1);
 75     ll lb = 1,ub = V;
 76     
 77     if(!C(t[ub]))
 78     {
 79         printf("AFK\n");
 80         return ;
 81     }
 82     while(ub - lb > 1)
 83     {
 84         int mid =  lb+(ub-lb)/2;
 85         if(C(t[mid])) ub = mid;
 86         else lb = mid;
 87     }
 88     if(C(t[lb]))
 89         write(t[lb]);
 90     else
 91         write(t[ub]);
 92 }
 93 int main()
 94 {
 95 //    freopen("testdata (1).in","r+",stdin);
 96     
 97     V = read(),E = read(),B = read();
 98     _for(i,1,V+1)
 99     {    f[i] = read();}
100 //    scanf("%d %d %d",&V,&E,&st);
101     _for(i,0,E)
102     {
103         ll s,t,c;
104         s = read(),t = read(),c = read();
105         //  scanf("%d %d %d",&s,&t,&c);
106         G[s].push_back(edge{t,c});
107         G[t].push_back(edge{s,c});
108         
109     }
110     
111     solve();
112     
113     //printf("%d ",d[i]);
114     return 0;
115 }