bzoj2662

#include<bits/stdc++.h>
using namespace std;  
const int N=105;  
int n,m,k,in1,in2,in3,f[N][N],ans=1e9,used[N];  
vector<pair<int,int> > graph[N];  
queue<int> q;  
void spfa(int s)  
{  
    for (int i=1;i<=n;i++)  
     for (int j=0;j<=k;j++)f[i][j]=1e9;  
    f[s][0]=0;  
    used[s]=1;  
    q.push(s);  
    while (!q.empty())  
     {  
        int x=q.front(),len=graph[x].size();  
        q.pop();  
        used[x]=0;  
        for (int i=0;i<len;i++)  
         {  
            int relaxed=0;  
            int t=graph[x][i].first,w=graph[x][i].second;  
            for (int j=0;j<=k;j++)  
             { 
                if(f[t][j]>f[x][j]+w) f[t][j]=f[x][j]+w,relaxed=1;  
                if(j&&f[t][j]>f[x][j-1]+(w>>1))
                 f[t][j]=f[x][j-1]+(w>>1),relaxed=1;
             }
            if (relaxed&&!used[t])
             {  
                used[t]=1;  
                q.push(t);
             }
         }  
     }  
}  
int main()  
{
    scanf("%d%d%d",&n,&m,&k);
    for (int i=1;i<=m;i++)
     {
        scanf("%d%d%d",&in1,&in2,&in3);
        graph[in1].push_back(make_pair(in2,in3));
        graph[in2].push_back(make_pair(in1,in3));
     }
    spfa(1);
    for(int i=0;i<=k;i++)ans=min(ans,f[n][i]);
    printf("%d\n",ans);
}