HDU 1839 Delay Constrained Maximum Capacity Path(dijkstra+二分)

#include <bits/stdc++.h>
#define maxn 20005
#define maxm 100005
#define ll long long
#define inf 0x3f3f3f3f
using namespace std;
struct Node{
  int to,w,val,next;
  bool operator < (const Node &a) const{
    return a.w < w;
  }
}Edge[maxm],Now,Next;
int head[maxm],num;
int T,n,m,t;

void init(){
  memset(head,-1,sizeof(head));
  num = 0;
}

void add(int u,int v,ll val,int w){
  Edge[num].w = w;
  Edge[num].val = val;
  Edge[num].to = v;
  Edge[num].next = head[u];
  head[u] = num ++;
}

bool dijkstra(ll val){
  int dist[maxn];
  bool vis[maxn];
  memset(vis,false,sizeof(vis));
  memset(dist,inf,sizeof(dist));
  dist[1] = 0;
  Now.to = 1;
  priority_queue<Node> q;
  q.push(Now);
  while(!q.empty()){
    Now = q.top();
    q.pop();
    int ans = Now.to;
    if(vis[ans] == true) continue;
    vis[ans] = true;
    for(int i=head[ans];i!=-1;i=Edge[i].next){
      int u = Edge[i].to;
      if(val <= Edge[i].val && !vis[u] && dist[u] > dist[ans] + Edge[i].w){
        dist[u] = dist[ans] + Edge[i].w;
        Next.to = u;
        Next.w = dist[u];
        q.push(Next);
      }
    }
  }
  return dist[n] <= t;
}

int main()
{
  scanf("%d",&T);
  while(T--){
    init();
    ll mi = 2000000000, mx = 0;
    scanf("%d%d%d",&n,&m,&t);
    for(int i=0;i<m;i++){
      int u,v,w;
      ll val;
      scanf("%d%d%lld%d",&u,&v,&val,&w);
      add(u, v, val, w);
      add(v, u, val, w);
      mi = min(mi, val);
      mx = max(mx, val);
    }
    ll ans = -1;
    ll l = mi, r = mx, mid;
    while(l <= r){
      ll mid = (l + r) >> 1;
      if(dijkstra(mid)){
        ans = mid;
        l = mid + 1;
      }
      else{
        r = mid - 1;
      }
    }
    printf("%lld\n",ans);
  }
  return 0;
}