Go: package main

import (
	"container/heap"
	"fmt"
	"runtime"
)

type Node struct {
	NowPosition          int
	DiscountTicketTCount int
	Amount               int
}

type PriorityQueueNode []*Node

func (pq PriorityQueueNode) Len() int {
	return len(pq)
}

func (pq PriorityQueueNode) Less(i, j int) bool {
	return pq[i].Amount < pq[j].Amount
}

func (pq PriorityQueueNode) Swap(i, j int) {
	pq[i], pq[j] = pq[j], pq[i]
}

func (pq *PriorityQueueNode) Push(node interface{}) {
	*pq = append(*pq, node.(*Node))
}

func (pq *PriorityQueueNode) Pop() interface{} {
	old := *pq
	n := len(old)
	item := old[n-1]
	*pq = old[0 : n-1]
	return item
}

type Point struct {
	NextPoint int
	Fee       int
}

type Memo struct {
	NowPoint             int
	DiscountTicketTCount int
}

func main() {
	var c, n, m, s, d int
	var a, b, f int

	for {
		fmt.Scan(&c, &n, &m, &s, &d)
		if c == 0 && n == 0 && m == 0 && s == 0 && d == 0 {
			break
		}
		s--
		d--
		pointMap := make([][]Point, n)
		for i := 0; i < n; i++ {
			pointMap[i] = make([]Point, 0, n)
		}
		for i := 0; i < m; i++ {
			fmt.Scan(&a, &b, &f)
			a--
			b--
			pointMap[a] = append(pointMap[a], Point{NextPoint: b, Fee: f})
			pointMap[b] = append(pointMap[b], Point{NextPoint: a, Fee: f})
		}
		pq := make(PriorityQueueNode, 0, m)
		start := Node{NowPosition: s, DiscountTicketTCount: c, Amount: 0}
		heap.Push(&pq, &start)
		memo := make(map[Memo]struct{})
		for len(pq) != 0 {
			now := heap.Pop(&pq).(*Node)
			if now.NowPosition == d {
				fmt.Println(now.Amount)
				break
			}
			memo[Memo{NowPoint: now.NowPosition, DiscountTicketTCount: now.DiscountTicketTCount}] = struct{}{}
			for _, v := range pointMap[now.NowPosition] {
				next := &Node{v.NextPoint, now.DiscountTicketTCount, now.Amount + v.Fee}
				if _, ok := memo[Memo{NowPoint: v.NextPoint, DiscountTicketTCount: now.DiscountTicketTCount}]; !ok {
					heap.Push(&pq, next)
				}
				if now.DiscountTicketTCount > 0 {
					next = &Node{v.NextPoint, now.DiscountTicketTCount - 1, now.Amount + v.Fee/2}
					if _, ok := memo[Memo{NowPoint: v.NextPoint, DiscountTicketTCount: now.DiscountTicketTCount}]; !ok {
						heap.Push(&pq, next)
					}
				}
			}
		}
		runtime.GC()
	}
}

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

using namespace std;

#define loop(i,a,b) for(int i=(a); i<(int)(b); i++)
#define rep(i,b) loop(i,0,b)

struct edge {
    int to, cost;
};

struct state {
    int v, d, rest;
    bool operator<(const state& s)const{
        return d>s.d;
    }
};

int dijk(int s, int g, vector<vector<edge>> G, int c){

    vector<int> d(G.size(), 1 << 30);
    d[s] = 0;
    priority_queue<state> q;
    q.push({ s, 0, c });

    while (q.size()){
        state sta = q.top();
        q.pop();

        int v = sta.v;

        if (d[v] > sta.d) continue;

        int rest = sta.rest;
        rep(i, G[v].size()){
            int to = G[v][i].to;
            int cost = G[v][i].cost;

            if (d[to] > sta.d + cost){
                d[to] = sta.d + cost;
                q.push({ to, sta.d + cost, rest});
            }

            if (!!rest && d[to] > sta.d + cost/2){
                d[to] = sta.d + cost / 2;
                q.push({ to, sta.d + cost / 2, rest - 1 });
            }
        }
    }
    return d[g];
}

int main(){
    while (1){
        int c, V, E, s, d;
        cin >> c >> V >> E >> s >> d;
        if (V == 0) break;
        vector<vector<edge>> G(V);
        s--; d--;
        rep(i, E){
            int a, b, c;
            cin >> a >> b >> c;
            a--; b--;
            G[a].push_back({ b, c });
            G[b].push_back({ a, c });
        }
        cout << dijk(s, d, G, c) << endl;
    }
}

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

using namespace std;

const int INF = 10000000;

int city[101][101];

int solve( int s, int d, int c, int n ){
	int dist[11][101];
	int history[101];

	for( int i = 0;i < 11;i++ ){
		for( int j = 1;j < 101;j++ ){
			dist[i][j] = INF;
		}
	}

	for( int i = 1;i < 101;i++ ){
		history[i] = 0;
	}

	for( int i = 0;i < 11;i++ ) dist[i][s] = 0;

	typedef pair<int,int> data;
	typedef pair<int,data> graph;
	priority_queue<graph,vector<graph>,greater<graph> > q;

	q.push( graph( 0, data( s, c ) ) );

	while( !q.empty() ){
		graph a = q.top();
		int u = a.second.first;
		int uc = a.second.second;
		q.pop();
		history[u] = 1;

		for( int i = 1;i <= n;i++ ){

			if( history[i] ) continue;
			if( dist[uc][i] > dist[uc][u] + city[u][i] ){
				dist[uc][i] = dist[uc][u] + city[u][i];
				q.push( graph( dist[uc][i], data( i, uc ) ) );
			}

			if( uc && dist[uc - 1][i] > dist[uc][u] + city[u][i] / 2 ){
				dist[uc - 1][i] = dist[uc][u] + city[u][i] / 2;
				q.push( graph( dist[uc - 1][i], data( i, uc - 1 ) ) );
			}
		}
	}
	int answer = INF;
	for( int i = 0;i < 11;i++ ) answer = min( dist[i][d], answer );
	return answer;

}

int main(int argc, char const* argv[])
{
	int c,n,m,s,d;

	while( cin >> c >> n >> m >> s >> d && c != 0 ){
		int a,b,f;
		for( int i = 1;i < 101;i++ ){
			for( int j = 1;j < 101;j++ ){
				city[i][j] = INF * 2;
			}
		}
		for( int i = 0;i < m;i++ ){
			cin >> a >> b >> f;
			city[a][b] = f;
			city[b][a] = f;
		}

		cout << solve( s, d, c, n ) << endl;
	}

	return 0;
}

C++: #include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <numeric>
using namespace std;

#define NONE -1

int c,n,m,s,d;
vector < vector <int> > P;
vector < vector <int> > E;
vector <int> R;
vector <bool> V;
int answer;

void solve( int t )
{
	if ( t == d )
	{
		sort( R.rbegin(), R.rend() );
		for ( int i = 0; i < min(c,R.size()); i++ )
		{
			R[i] /= 2;
		}
		if ( answer == -1 )
			answer = accumulate( R.begin(), R.end(), 0 );
		else
			answer = min( answer, accumulate( R.begin(), R.end(), 0 ) );
	}
	else
	{
		V[t] = true;
		for ( vector <int>::iterator it = E[t].begin(); it != E[t].end(); it++ )
		{
			if ( V[*it] == false )
			{
				R.push_back( P[t][*it] );
				solve(*it);
				R.pop_back();
			}
		}
		V[t] = false;
	}
}

int main( void )
{
	while ( cin >> c >> n >> m >> s >> d && c && n && m && s && d )
	{
		s--;
		d--;
		P = vector < vector <int> >(n+1, vector <int>(n+1,NONE));
		E = vector < vector <int> >(n+1);
		for ( int i = 0; i < m; i++ )
		{
			int a, b, f;
			cin >> a >> b >> f;
			P[a-1][b-1] = f;
			P[b-1][a-1] = f;
			E[a-1].push_back( b-1 );
			E[b-1].push_back( a-1 );
		}

		R = vector <int>();
		V = vector <bool>(n+1,false);
		answer = -1;
		solve( s );
		cout << answer << endl;
	}

	return 0;
}