HDU 4479 权递增的最短路问题

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 #include <iostream>
 5 using namespace std;
 6 const int N = 10005;
 7 typedef long long LL;
 8 LL dp[N];
 9 int n , m , k;
10 
11 struct Path{
12     int x,y,d;
13     bool operator<(const Path &m)const{
14         return d < m.d;
15     }
16 }p[100005];
17 
18 struct Rec{
19     int x,y;
20     LL d;
21     Rec(int x=0,int y=0,LL d=0):x(x),y(y),d(d){}
22 }rec[100005];
23 
24 void update(int l , int r)
25 {
26     int t = 0;
27 
28     for(int i=l;i<=r;i++){
29         int u = p[i].x , v = p[i].y;
30         if(dp[u] >= 0 && (dp[v] > dp[u] + p[i].d || dp[v] < 0))
31         {
32             rec[t++] = Rec(u,v, dp[u] + p[i].d);
33         }
34         if(dp[v] >= 0 && (dp[u] > dp[v] + p[i].d || dp[u] < 0))
35         {
36             rec[t++] = Rec(v,u, dp[v] + p[i].d);
37         }
38     }
39 
40     for(int i=0;i<t;i++){
41         int u = rec[i].x , v = rec[i].y;
42         if(dp[v] > rec[i].d || dp[v] < 0)
43         {
44             dp[v] = rec[i].d;
45         }
46     }
47 }
48 
49 void add_edge(int x,int y,int d)
50 {
51     p[k].x = x , p[k].y = y , p[k++].d = d;
52 }
53 
54 void solve()
55 {
56     sort(p,p+k);
57     memset(dp,-1,sizeof(dp));
58     dp[1] = 0;
59     int l=0;
60     for(int r=1 ; r<k;r++){
61         if(p[r].d != p[r-1].d){
62             update(l , r-1);
63             l=r;
64         }
65     }
66     update(l,k-1);
67     if(dp[n] < 0)
68         puts("No answer");
69     else
70         printf("%I64d\n",dp[n]);
71 }
72 
73 int main()
74 {
75    // freopen("test.in","rb",stdin);
76 
77     int T,a,b,d;
78     scanf("%d",&T);
79     while(T--){
80         scanf("%d%d",&n,&m);
81 
82         k=0;
83         memset(G , -1 , sizeof(G));
84         for(int i=0;i<m;i++){
85             scanf("%d%d%d",&a,&b,&d);
86             add_edge(a,b,d);
87         }
88         solve();
89     }
90     return 0;
91 }