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 <queue>
#include <vector>
#include <functional>

using namespace std;

const int INF = 10000000;

int solve( int city[101][101], 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 = 0;j < 101;j++ ){
			dist[i][j] = INF;
		}
	}

	for( int i = 0;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( 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][i] + 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;
	int city[101][101];

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

	return 0;
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#define INF 1000000000;
#define dis first
#define mati second.first
#define sta  second.second
using namespace std;
typedef pair <int ,pair <int,int> > P;
vector <P> mp[102];
int c,n,m,start,goal;

int dijkstra() {
  int flg[12][102] = {},dis[12][102];
  for(int j=0;j<=c;j++)
    for(int i=0;i<=n;i++) dis[j][i] = -INF;

  for(int j=1;j<=c;j++)flg[j][start] = 1;

  priority_queue <P> Q;
  P t;
  t.dis = 0, t.mati = start, t.sta = 0;
  Q.push(t);

  while(!Q.empty()) {
    t = Q.top(),Q.pop();
    if(flg[t.sta][t.mati] == 1) continue;
    flg[t.sta][t.mati] = 1;
    for(int i=0;i<mp[t.mati].size();i++){
      int ndis = mp[t.mati][i].dis;
      int nmati = mp[t.mati][i].mati;
      int nsta = t.sta+1;
      P tt;
      if(dis[t.sta][nmati] < t.dis-ndis && flg[t.sta][nmati] == 0) {
	tt.dis = t.dis-ndis,tt.mati = nmati,tt.sta = t.sta;
	dis[t.sta][nmati] = t.dis-ndis;
	Q.push(tt);
      }
      if(nsta<= c&&dis[nsta][nmati]<t.dis-ndis/2 && flg[nsta][nmati]==0){
	tt.dis = t.dis - ndis/2 , tt.mati = nmati, tt.sta = nsta;
	dis[nsta][nmati] = t.dis-ndis/2;
	Q.push(tt);
      }
    }
  }

  int ans = -INF;
  for(int j=0;j<=c;j++)ans = max(ans,dis[j][goal]);
   
  return -ans;
}


int main() {
  while(1) {
    cin >> c >> n >> m >> start >> goal;
    if(c==0&&n==0&&m==0&&start==0&&goal==0) break;

    for(int i=0;i<=n;i++) mp[i].clear();
    for(int i=0;i<m;i++) {
      int a,b,f;
      cin >> a >> b >> f;
      P t;
      t.dis = f,  t.mati = b , t.sta = 0;
      mp[a].push_back(t);
      t.mati = a;
      mp[b].push_back(t);
    }

    cout << dijkstra() << endl;
  }

  return 0;
}

C++: #include <iostream>
#include <string>
#include <sstream>
#include <vector>
#include <iterator>
#include <cstdlib>
#include <algorithm>
using namespace std;

typedef vector<int> vint;

vint input(int sz){
	string s;
	getline(cin, s);
	stringstream ss1(s), ss2;
	istream_iterator<int> b(ss1), e;
	vint v(b, e);
	if(cin.eof() || v.size() != sz){ throw ""; }
	for(int i = 0; i < sz; ++i){
		if(i){ ss2 << ' '; }
		ss2 << v[i];
	}
	string t = ss2.str();
	if(s != t){ throw 0; }
	return v;
}

int main(){
	while(1){
		vint v = input(5);
		if(!v[0] && !v[1] && !v[2] && !v[3] && !v[4]){ break; }
		for(int i = 0; i < v[2]; ++i){
			input(3);
		}
	}

	cin.peek();
	if(!cin.eof()){
		exit(EXIT_FAILURE);
	}
}

C++: #include<iostream>
#include<vector>
#include<algorithm>
#include<queue>
#include<climits>

using namespace std;

typedef pair<int,pair<int,int> >P;

struct Edge{
  int to,cost;
  Edge(int _to, int _cost):to(_to), cost(_cost){};
};

int minCost[101][11];
vector<Edge> edge[101];
static const int INF = INT_MAX;

int c,n,m,s,d;

int dijkstra(void){
  priority_queue<P, vector<P>, greater<P> >que;
  que.push(make_pair(0,make_pair(s,c)));

  for(int i=0;i<101;i++)
    for(int j=0;j<11;j++)
      minCost[i][j]=INF;

  while(!que.empty()){
    P p = que.top();
    que.pop();
    
    for(int i=0;i<edge[p.second.first].size();i++){
      Edge e = edge[p.second.first][i];
      if(p.first+e.cost < minCost[e.to][p.second.second]){
	minCost[e.to][p.second.second] = p.first+e.cost;
	que.push(make_pair(p.first+e.cost,make_pair(e.to,p.second.second)));
      }
    }
    
    if(p.second.second==0)continue;
    
    for(int j=0;j<edge[p.second.first].size();j++){
      Edge e = edge[p.second.first][j];
      if(p.first+e.cost/2 < minCost[e.to][p.second.second-1]){
	minCost[e.to][p.second.second-1] = p.first+e.cost/2;
	que.push(make_pair(p.first+e.cost/2,make_pair(e.to,p.second.second-1)));
      }
    }
  }
  int ans=INT_MAX;
  for(int i=0;i<11;i++)
    ans=min(minCost[d][i],ans);

  return ans;
}

int main(void){
  int a,b,f;

  while(cin >> c >> n >> m >> s >> d,c|n|m|s|d){

    for(int i=0;i<=n;i++)edge[i].clear();

    for(int i=0;i<m;i++){
      cin >> a >> b >> f;
      edge[a].push_back(Edge(b,f));
      edge[b].push_back(Edge(a,f));
    }

    cout << dijkstra() << endl;
  }

  return 0;
}