Go: package main

import (
	"bufio"
	"fmt"
	"math"
	"os"
	"strconv"
	"strings"
)

var scanner = bufio.NewScanner(os.Stdin)

const INF = 0x7FFFFFFF

var pass [][]int

func main() {
	for scanner.Scan() {
		pass = make([][]int, 200)
		for i := range pass {
			pass[i] = make([]int, 200)
		}
		buf := strings.Split(scanner.Text(), " ")
		c, _ := strconv.Atoi(buf[0])
		n, _ := strconv.Atoi(buf[1])
		m, _ := strconv.Atoi(buf[2])
		s, _ := strconv.Atoi(buf[3])
		d, _ := strconv.Atoi(buf[4])
		if c == 0 && n == 0 && m == 0 && s == 0 && d == 0 {
			break
		}
		s--
		d--
		for i := 0; i < 200; i++ {
			for j := 0; j < 200; j++ {
				pass[i][j] = INF
			}
		}
		for i := 0; i < 200; i++ {
			pass[i][i] = 0
		}
		for i := 0; i < m; i++ {
			scanner.Scan()
			buf_ := strings.Split(scanner.Text(), " ")
			a, _ := strconv.Atoi(buf_[0])
			b, _ := strconv.Atoi(buf_[1])
			f, _ := strconv.Atoi(buf_[2])
			a--
			b--
			pass[a][b] = f
			pass[b][a] = f
		}
		fmt.Println(dijkstra(s, d, c, n))
	}
}

func dijkstra(s, g, c, n int) float64 {
	d := make([][]float64, 200)
	used := make([][]bool, 200)
	for i := 0; i < 200; i++ {
		d[i] = make([]float64, 20)
		used[i] = make([]bool, 20)
	}
	for i := range d {
		for j := range d[i] {
			d[i][j] = INF
		}
	}
	d[s][c] = 0
	for {
		v := -1
		w := -1
		for u := 0; u < n; u++ {
			for i := 0; i < c+1; i++ {
				if !used[u][i] && (v == -1 || d[u][i] < d[v][w]) {
					v = u
					w = i
				}
			}
		}
		if v == -1 {
			break
		}
		used[v][w] = true
		for u := 0; u < n; u++ {
			d[u][w] = math.Min(d[u][w], d[v][w]+float64(pass[v][u]))
			if w-1 >= 0 && pass[v][u] != INF {
				d[u][w-1] = math.Min(d[u][w-1], d[v][w]+(float64(pass[v][u]/2.0)))
			}
		}
	}
	ret := float64(INF)
	for i := 0; i < c+1; i++ {
		ret = math.Min(ret, d[g][i])
	}
	return ret
}

C++: #include <iostream>
#include <vector>
#include <queue>
#include <tuple>

using namespace std;

const int INF = 1<<28;
int c, n, m, s, d;
vector<pair<int, int> > g[100];
int dist[100][11];

typedef tuple<int, int, int> node;

int dijkstra() {
  priority_queue<node, vector<node>, greater<node> > Q;
  Q.push({0, s, c});
  dist[s][c] = 0;
  
  while (!Q.empty()) {
    int cost;
    int v;
    int t;
    tie(cost, v, t) = Q.top();
    Q.pop();
    for (auto &edge: g[v]) {
      int w = edge.first;
      int weight = edge.second;
      if (cost + weight < dist[w][t]) {
        dist[w][t] = cost + weight;
        Q.push({dist[w][t], w, t});
      }
      if (t > 0 && cost + weight/2 < dist[w][t-1]) {
        dist[w][t-1] = cost + weight/2;
        Q.push({dist[w][t-1], w, t-1});
      }
    }
  }

  int ret = INF;
  for (int i = 0; i < 11; i++)
    ret = min(ret, dist[d][i]);
  return ret;
}

void init() {
  for (int i = 0; i < 100; i++)
    g[i].clear();
  for (int i = 0; i < 100; i++)
    for (int j = 0; j < 11; j++)
      dist[i][j] = INF;
}

int main(int argc, char *argv[])
{
  for (;;) {
    cin >> c >> n >> m >> s >> d;
    if (!c && !n && !m && !s && !d)
      break;
    --s, --d;
    init();
    for (int i = 0; i < m; i++) {
      int a, b, f;
      cin >> a >> b >> f;
      --a, --b;
      g[a].push_back({b, f});
      g[b].push_back({a, f});
    }
    int ret = dijkstra();
    printf("%d\n", ret);
  }
  
  return 0;
}

C++: #include <map>
#include <vector>
#include <cstdio>
#include <cstring>
using namespace std;
int cost[101][11];
int main(){
	int c,N,m,s,d,i,j,k,x;
	for(;scanf("%d%d%d%d%d",&c,&N,&m,&s,&d),N;){
		vector<map<int,int> >dist(N+1);
		memset(cost,99,sizeof(cost));
		for(k=0;k<m;k++){
			scanf("%d%d%d",&i,&j,&x);dist[i][j]=dist[j][i]=x;
		}
		for(i=0;i<=c;i++)cost[s][i]=0;
		for(c=0;~c;c--){
			vector<bool>used(N+1);
			for(;;){ //dijkstra
				int m=9999999;
				for(i=1;i<=N;i++)if(!used[i]&&m>cost[i][c])m=cost[i][c];
				if(m==9999999)break;
				for(j=1;j<=N;j++)if(m==cost[j][c]){
					map<int,int>::iterator it=dist[j].begin();
					for(used[j]=1;it!=dist[j].end();it++){
						if(cost[it->first][c]>it->second+cost[j][c])cost[it->first][c]=it->second+cost[j][c];
						if(c&&cost[it->first][c-1]>it->second/2+cost[j][c])cost[it->first][c-1]=it->second/2+cost[j][c];
					}
				}
			}
		}
		printf("%d\n",cost[d][0]);
	}
}

C++: #include <bits/stdc++.h>
using namespace std;

typedef pair<int,int>P;

int C[105][15];



int main(){
	
	int c,n,m,s,d;
	while(cin>>c>>n>>m>>s>>d,c){
		vector<P>V[105];
		
		for(int i=0;i<105;i++){
			for(int j=0;j<15;j++)C[i][j]=1145141919;
		}
		
		for(int i=0;i<m;i++){
			int x,y,z;
			cin>>x>>y>>z;
			V[x].push_back(P(y,z));
			V[y].push_back(P(x,z));
		}
		
		priority_queue<P , vector<P> , greater<P> >Q;
		
		Q.push(P(0,c*1000+s));
		
		while(!Q.empty()){
			int cost=Q.top().first;
			int pos=Q.top().second%1000;
			int card=Q.top().second/1000;
			Q.pop();
			
			if(pos==d){
				cout<<cost<<endl;
				break;
			}
			if(C[pos][card]!=1145141919){
				continue;
			}
			
			//cout<<"#"<<pos<<" "<<card<<" "<<cost<<endl;
			
			C[pos][card]=cost;
			for(int i=0;i<V[pos].size();i++){
				//cout<<"$$"<<V[pos][i].first<<" "<<V[pos][i].second<<endl;
				if(card>0){
					if(C[V[pos][i].first][card-1]==1145141919){
						Q.push(P(cost+V[pos][i].second/2,(card-1)*1000+V[pos][i].first));
					}
				}
				if(C[V[pos][i].first][card]==1145141919){
					Q.push(P(cost+V[pos][i].second,card*1000+V[pos][i].first));
				}
			}
			
		}
		
	}
	
	
	
	return 0;
}

C++: #include<queue>
#include<cstdio>
#include<algorithm>

#define	mp	make_pair

using namespace std;

typedef	pair<int,int>	pii;

const int inf=1<<29;
int adj[100][100],memo[100][11];
bool visited[100][11];

int main(){
	for(int c,m,n,src,dst;scanf("%d%d%d%d%d",&c,&m,&n,&src,&dst),c;){
		src--,dst--;
		for(int i=0;i<n;i++)for(int j=0;j<n;j++)	adj[i][j]=(i==j?0:inf);
		for(int i=0;i<n;i++)for(int j=0;j<=c;j++)	memo[i][j]=inf,visited[i][j]=false;
		for(int i=0;i<m;i++){
			int a,b,fee;	scanf("%d%d%d",&a,&b,&fee);
			a--,b--;
			adj[a][b]=adj[b][a]=fee;
		}

		memo[src][0]=0;
		priority_queue< pair<int,pii> > pq;	pq.push(mp(0,mp(src,0)));
		while(!pq.empty()){
			pair<int,pii> a=pq.top();	pq.pop();
			int fee=-a.first;
			int u=a.second.first;
			int tic=a.second.second;
			if(u==dst)	break;

			if(visited[u][tic])	continue;
			visited[u][tic]=true;

			for(int v=0;v<n;v++){
				if(!visited[v][tic] && fee+adj[u][v]<memo[v][tic]){
					memo[v][tic]=fee+adj[u][v];
					pq.push(mp(-memo[v][tic],mp(v,tic)));
				}
				if(!visited[v][tic+1] && fee+adj[u][v]/2<memo[v][tic+1] && tic<c){
					memo[v][tic+1]=fee+adj[u][v]/2;
					pq.push(mp(-memo[v][tic+1],mp(v,tic+1)));
				}
			}
		}

		int feemin=inf;
		for(int i=0;i<=c;i++)	feemin=min(feemin,memo[dst][i]);
		printf("%d\n",feemin);
	}

	return 0;
}