Go: package main

import (
	"container/heap"
	"fmt"
)

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]int)
		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}] = now.Amount
			for _, v := range pointMap[now.NowPosition] {
				next := &Node{v.NextPoint, now.DiscountTicketTCount, now.Amount + v.Fee}
				if memoAmount, ok := memo[Memo{NowPoint: v.NextPoint, DiscountTicketTCount: now.DiscountTicketTCount}]; !ok || (ok && memoAmount > next.Amount) {
					memo[Memo{NowPoint: v.NextPoint, DiscountTicketTCount: now.DiscountTicketTCount}] = next.Amount
					heap.Push(&pq, next)
				}
				if now.DiscountTicketTCount > 0 {
					next = &Node{v.NextPoint, now.DiscountTicketTCount - 1, now.Amount + v.Fee/2}
					if memoAmount, ok := memo[Memo{NowPoint: v.NextPoint, DiscountTicketTCount: now.DiscountTicketTCount}]; !ok || (ok && memoAmount > next.Amount) {
						memo[Memo{NowPoint: v.NextPoint, DiscountTicketTCount: now.DiscountTicketTCount}] = next.Amount
						heap.Push(&pq, next)
					}
				}
			}
		}
		//runtime.GC()
	}
}

C++: #include <stdio.h>
#include <cmath>
#include <algorithm>
#include <stack>
#include <queue>
#include <vector>
typedef long long int ll;

using namespace std;

int minimum,num_ticket,num_town,m,start,goal,costTable[101][101];


struct Info{
	Info(){
		for(int i = 1; i <= num_town; i++){
			visited[i] = false;
		}
		current_town = 0;
		index = 0;
	}
	bool visited[102];
	int current_town,index,costs[102];

};

void func(Info info){

	//?¢?????????????????¨??????????<???info.costs????????????????????§???????????¨????????????>
	int sum = 0;

	for(int i = 0; i < info.index;i++){
		if(i < num_ticket){
			sum += info.costs[i]/2;
		}else{
			sum += info.costs[i];
		}
	}

	if(info.current_town == goal){ //?????¨????¢????????????????????°????????¶????????????????????????????
		minimum = min(minimum,sum);
		return;
	}else{
		if(sum >= minimum){
			return;
		}
	}

	for(int i = 1; i <= num_town; i++){
		if(costTable[info.current_town][i] != -1 && info.visited[i] == false){ //??????????????¨?????????????¨????????????¨???????????´???
			Info new_info;
			for(int k = 1; k <= num_town; k++)new_info.visited[k] = info.visited[k];
			new_info.visited[i] = true;
			new_info.current_town = i;
			for(int k = 0; k < info.index;k++)new_info.costs[k] = info.costs[k];

			//?????\?????????
			if(info.index == 0 || info.costs[info.index-1] <= costTable[info.current_town][i]){
				new_info.costs[info.index] = costTable[info.current_town][i];
				new_info.index = info.index+1;
				func(new_info);
			}else{
				for(int k = 0; k < info.index; k++){
					if(new_info.costs[k] < costTable[info.current_town][i]){
						for(int p = info.index-1; p >= k; p--){
							new_info.costs[p+1] = new_info.costs[p];
						}
						new_info.costs[k] = costTable[info.current_town][i];
						break;
					}
				}
				new_info.index = info.index+1;
				func(new_info);
			}
		}
	}
}

int main(){

	int from,to,fee;

	while(true){
		scanf("%d %d %d %d %d",&num_ticket,&num_town,&m,&start,&goal);
		if(num_ticket == 0 && num_town == 0 && m == 0 && start == 0 && goal == 0)break;

		minimum = 2000000000;

		for(int i = 1; i <= num_town; i++){
			for(int k = 1; k <= num_town; k++)costTable[i][k] = -1;
		}

		for(int i = 0; i < m; i++){
			scanf("%d %d %d",&from,&to,&fee);
			costTable[from][to] = fee;
			costTable[to][from] = fee;
		}

		Info info;

		info.current_town = start;
		info.visited[start] = true;

		func(info);

		printf("%d\n",minimum);
	}


	return 0;
}

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

#define INF 1010000000
#define rep(i,n) for(int i=0;i<n;i++)
#define reps(i,n) for(int i=1;i<=n;i++)
#define sint(i) scanf("%d",&i);
#define sintt(i,j) scanf("%d%d",&i,&j);
#define sinttt(i,j,k) scanf("%d%d%d",&i,&j,&k);

using namespace std;

class S{
	public:
	int p;
	int v;
	int n;
	
	S(int p,int v,int n):p(p),v(v),n(n){}
	
	bool operator<(const S&a)const{
		return v>a.v;
		return v==a.v ? v>a.v : n <a.n;
	}
};

int main(){
	while(1){
		int c,n,m,s,g;
		scanf("%d%d%d%d%d",&c,&n,&m,&s,&g);
		if(c==0&&n==0)break;
		
		int root[101][101];
		rep(i,101)rep(j,101)root[i][j]=INF;
		
		rep(i,m){
			int a,b,d;
			sinttt(a,b,d);
			root[a][b]=d;
			root[b][a]=d;
		}
		
		priority_queue<S> qui;
		qui.push(S(s,0,0));
		int ans=0;
		
		int visit[101][11];
		rep(i,101)rep(j,11)visit[i][j]=0;
		
		while(1){
			if(qui.empty()==1){
				ans=-1;
				break;
			}
			
			S u=qui.top();qui.pop();
			
			if(u.p==g){
				ans=u.v;
				break;
			}
			
			//printf("%d %d %d\n",u.p,u.v,u.n);
			visit[u.p][u.n]=1;
			
			reps(i,n){
				if(root[u.p][i]!=INF){
					if(visit[i][u.n]==0){
						qui.push(S(i,u.v+root[u.p][i],u.n));
					}
					if(visit[i][u.n+1]==0 && visit[u.p][u.n+1]==0 && u.n+1 <= c){
						qui.push(S(i,u.v+root[u.p][i]/2,u.n+1));
					}
				}
			}
		}
		printf("%d\n",ans);
	}
}