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
}

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)
		}
		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)
		start := Node{NowPosition: s, DiscountTicketTCount: c, Amount: 0}
		heap.Push(&pq, &start)
		for len(pq) != 0 {
			now := heap.Pop(&pq).(*Node)
			if now.NowPosition == d {
				fmt.Println(now.Amount)
				break
			}
			for _, v := range pointMap[now.NowPosition] {
				next := &Node{v.NextPoint, now.DiscountTicketTCount, now.Amount + v.Fee}
				heap.Push(&pq, next)
				if now.DiscountTicketTCount > 0 {
					next = &Node{v.NextPoint, now.DiscountTicketTCount - 1, now.Amount + v.Fee/2}
					heap.Push(&pq, next)
				}
			}
		}
	}
}

C++: #include <bits/stdc++.h>
using namespace std;
#define FOR(i, s, n) for(int i = s; i < (int)n; i++)
#define per(i, n) for(int i = n; i >= 0; i--)
#define ROF(i, s, n) for(int i = s; i >= (int)n; i--)
#define FORIT(i, A) for (auto i : A)
#define PRINT(x) cout << (x) << "\n"
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define MP make_pair
#define EACH(i, n) for (__typeof((n).begin()) i = (n).begin(); i != (n).end(); ++i)
#define SZ(a) int((a).size())
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())
#define CLR(a) memset((a), 0 ,sizeof(a))
#define NCLR(a) memset((a), -1 ,sizeof(a))
#define dump(x) cout << #x << " = " << (x) << "\n";
#define debug(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << "\n";
#define sq(n) (n) * (n)
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef priority_queue<int> maxpq;
typedef priority_queue< int, vector<int>, greater<int> > minpq;
typedef complex<double> P;
static const double EPS = 1e-10;
static const double PI = acos( -1.0 );
static const int mod = 1000000007;
static const int INF = 1 << 29;
static const LL LL_INF = 1152921504606846976;
static const int dx[] = { -1, 0, 1, 0, 1, -1, 1, -1 };
static const int dy[] = { 0, -1, 0, 1, 1, 1, -1, -1 };
int c, n, m, s, d, ans;
vector<vector<PII> > v;
int dp[ 11 ][ 100 ];
bool check[ 11 ][ 100 ];

struct Union_Find {
	vector<int> par;
	vector<int> rank;

	void init( int n ) {
		par.resize( n );
		rank.resize( n );
		for ( int i = 0; i < n; ++i ) {
			par[ i ] = i;
			rank[ i ] = 0;
		}
	}
	int find( int s ) {
		if ( par[ s ] == s ) {
			return s;
		}
		return par[ s ] = find( par[ s ] );
	}
	void unite( int x, int y ) {
		int a = find( x ), b = find( y );
		if ( a == b ) {
			return;
		}
		if ( rank[ x ] < rank[ y ] ) {
			par[ x ] = y;
		}
		else {
			par[ y ] = x;
			if ( rank[ x ] == rank[ y ] ) {
				++rank[ x ];
			}
		}
	}
	bool same( int x, int y ) {
		return find( x ) == find( y );
	}
	unsigned int size() {
		return par.size();
	}
};

int solve( int canUseT, int now, Union_Find u ) {
	if ( now == d ) {
		return 0;
	}
	if ( dp[ canUseT ][ now ] >= 0 ) {
		return dp[ canUseT ][ now ];
	}
	if ( check[ canUseT ][ now ] ) {
		return INF;
	}
	u.unite( s, now );
	int res = INF;
	for ( int i = 0; i < v[ now ].size(); i++ ) {
		if ( u.same( now, v[ now ][ i ].first ) ) {
			continue;
		}
		if ( canUseT ) {
			res = min( res, solve( canUseT - 1, v[ now ][ i ].first, u ) + v[ now ][ i ].second / 2 );
		}
		res = min( res, solve( canUseT, v[ now ][ i ].first, u ) + v[ now ][ i ].second );
	}
	return dp[ canUseT ][ now ] = res;
}

int main() {
	Union_Find uf;
	while ( ~scanf( "%d %d %d %d %d", &c, &n, &m, &s, &d ) && c && n && m && s && d ) {
		s--;
		d--;
		v.resize( n );
		uf.init( n );
		NCLR( dp );
		CLR( check );
		for ( int i = 0; i < m; i++ ) {
			int a, b, f;
			scanf( "%d %d %d", &a, &b, &f );
			v[ a - 1 ].push_back( MP( b - 1, f ) );
			v[ b - 1 ].push_back( MP( a - 1, f ) );
		}
		ans = solve( c, s, uf );
		printf( "%d\n", ans );
		v.clear();
	}
	return 0;
}

C++: #include <iostream>
#include <algorithm>

  using namespace std;

  const int INF = 1000000000;

  int c, n, m, s, d;
  int visited[100][11];
  int edge[100][100];

  void dfs(int p, int rem, int cost){
    if(visited[p][rem] < cost) return;
    visited[p][rem] = cost;
    if(p == d) return;
    for(int i=0;i<n;i++){
      if(edge[p][i] == INF) continue;
      if(rem > 0 ) dfs(i, rem-1, cost+(edge[p][i]/2));
      dfs(i, rem, cost+edge[p][i]);
    }
  }


 main(){
    while(cin >> c >> n >> m >> s >> d && (c || n || m || s || d)){
      fill(edge[0], edge[100], INF);
      fill(visited[0], visited[100], INF);
      --s; --d;
      for(int i=0;i<m;i++){
         int a, b, f;
         cin >> a >> b >> f;
         --a; --b;
         edge[a][b] = edge[b][a] = f;
      }

      dfs(s, c, 0);
      int ans = INF;
      for(int i=0;i<c;i++){
         ans = min(ans, visited[d][i]);
      }

      cout << ans << endl;
    }

    return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

#define llong long long 
typedef pair<int, int> P;

typedef struct data{
	int now;
	int time;
	int dep;

	bool operator > (const data& right) const{
		return dep == right.dep ? time > right.time : dep > right.dep;
	}

}data;

int c, n, m, s, d;
vector<P> edges[101];
int cost[101][11];
priority_queue<data, vector<data>, greater<data> > q;

void solve(){
	data D;
	D.now = s;
	D.time = 0;
	D.dep = 0;
	q.push(D);

	while(!q.empty()){
		data nd = q.top(); q.pop();
		int nowp = nd.now;
		int nowtime = nd.time;
		int nowdep = nd.dep;

		if(cost[nowp][nowdep] < nowtime) continue;

		for(int i = 0; i < edges[nowp].size(); i++){
			P edge = edges[nowp][i];
			if(cost[edge.first][nowdep] > cost[nowp][nowdep] + edge.second){
				data in;
				in.now = edge.first;
				in.time = cost[nowp][nowdep] + edge.second;
				in.dep = nd.dep;
				cost[in.now][in.dep] = in.time;
				q.push(in);
			}

			if(nowdep < c){
				if(cost[edge.first][nowdep + 1] > cost[nowp][nowdep] + edge.second / 2){
					data in;
					in.now = edge.first;
					in.time = nowtime + (edge.second / 2);
					in.dep = nowdep + 1;
					cost[in.now][in.dep] = in.time;
					q.push(in);
				}			
			}

		}
	}

	return;
}

int main(){
	while(cin >> c >> n >> m >> s >> d, n){
		fill_n(*cost, 101 * 11, 99999999);
		for(int i = 0; i <= c; i++){
			cost[s][i] = 0;
		}
		for(int i = 0; i < m; i++){
			int n, to, cos;
			cin >> n >> to >> cos;
			edges[n].push_back(P(to, cos));
			edges[to].push_back(P(n, cos));
		}

		solve();

		cout << cost[d][c] << endl;


		for(int i = 0; i < 101; i++){
			edges[i].clear();
		}
	}

	return 0;
}