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 <iostream>
#include <vector>
#include <set>

using namespace std;

#define INF 100000000

typedef pair<int, int> P;

int main() {
	int c, n, m, s, d;
	while (cin >> c >> n >> m >> s >> d) {
		if (c == 0 && n == 0 && m == 0 && s == 0 && d == 0) {
			break;
		}
		vector< vector<int> > ff(n+1, vector<int>(n+1, INF));
		vector< vector<int> > ddd(101, vector<int>(101, INF));
		int a, b, f;
		for (int i = 0; i < m; i++) {
			cin >> a >> b >> f;
			ff[a][b] = ff[b][a] = f;
			ddd[a][b] = ddd[b][a] = f;
		}
		for (int i = 1; i <= n; i++) {
			ddd[i][i] = 0;
		}
		for (int k = 1; k <= n; k++) {
			for (int i = 1; i <= n; i++) {
				for (int j = 1; j <= n; j++) {
					ddd[i][j] = min(ddd[i][j], ddd[i][k]+ddd[k][j]);
				}
			}
		}
		vector< vector< vector<int> > > dp(101, vector< vector<int> >(101, vector<int>(11, INF)));
		for (int i = 1; i < 101; i++) {
			dp[i][i][0] = 0;
			dp[s][i][0] = ddd[s][i];
			dp[i][d][0] = ddd[i][d];
		}
		/*for (int i = 1; i <= n; i++) {
			for (int j = 1; j <= n; j++) {
				cout << ddd[i][j] << ' ';
			}
			cout << endl;
		}
		cout << endl;*/
		set<P> st[101][101][11];
		for (int k = 1; k <= c; k++) {
			for (int i = 1; i <= n; i++) {
				dp[s][i][k] = dp[s][i][k-1];
				dp[i][d][k] = dp[i][d][k-1];
				st[s][i][k] = st[s][i][k-1];
				st[i][d][k] = st[i][d][k-1];
				int ka, kb, kc, kd;
				ka = kb = kc = kd = 0;
				for (int j = 1; j <= n; j++) {
					for (int p = 1; p <= n; p++) {
						if (ff[j][p] != INF && st[s][i][k].find(P(j, p)) == st[s][i][k].end()) { //dd[s][i][k][j][p]
							if (dp[s][i][k] > dp[s][j][k-1]+(ff[j][p]/2)+ddd[p][i]) {
								dp[s][i][k] = dp[s][j][k-1]+(ff[j][p]/2)+ddd[p][i];
								ka = j;
								kb = p;
							}
						}
						if (ff[j][p] != INF && st[i][d][k].find(P(j, p)) == st[i][d][k].end()) { //dd[i][D][k][j][p]
							if (dp[i][d][k] > dp[i][j][k-1]+(ff[j][p]/2)+ddd[p][d]) {
								dp[i][d][k] = dp[i][j][k-1]+(ff[j][p]/2)+ddd[p][d];
								kc = j;
								kc = p;
							}
						}
					}
				}
				st[s][i][k].insert(P(ka, kb));
				st[i][d][k].insert(P(kc, kd));
				//dd[s][i][k][a][b] = dd[i][D][k][C][dk] = 1;
			}
			/*for (int i = 1; i <= n; i++) {
				for (int j = 1; j <= n; j++) {
					cout << dp[i][j][k] << ' ';
				}
				cout << endl;
			}
			cout << endl;*/
		}
		cout << dp[s][d][c] << endl;
	}
	return 0;
}

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

using namespace std;

struct P {
	int from, cost, coupon;

	bool operator >(const P& p) const {
		return cost > p.cost;
	}
};

int ecost[101][101];
int ccost[101][11];
int c, n, m, s, d;
int i;

int main() {
	while(cin >> c >> n >> m >> s >> d, c|n|m|s|d) {
		fill_n((int *)ecost, 101*101, -1);
		fill_n((int *)ccost, 101*11, 1e8);
		fill_n((int *)ccost, 11, 0);
		for(i=0; i<m; i++){
			int a, b, f;
			cin >> a >> b >> f;
			ecost[a][b] = f;
			ecost[b][a] = f;
		}
		priority_queue<P, vector<P>, greater<P>> q;
		q.push((P){s, 0, 0});
		int dcost;
		while(!q.empty()){
			P p = q.top(); q.pop();
			// cout << "pos=" << p.from << endl;
			// goal
			if(p.from == d) {
				dcost = p.cost;
				break;
			}
			//
			for(i=0; i<n+1; i++){ // i:to
				if(ecost[p.from][i] != -1){
					if(p.cost + ecost[p.from][i] < ccost[i][p.coupon]){
						q.push((P){i, p.cost + ecost[p.from][i], p.coupon});
					}
					if(p.coupon+1 <= c) {
						if(p.cost + ecost[p.from][i]/2 < ccost[i][p.coupon+1]){
							q.push((P){i, p.cost + ecost[p.from][i]/2, p.coupon+1});
						}
					}
				}
			}
		}
		cout << dcost << endl;
	}
	return 0;
}

C++: #include <iostream>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <string>
#include <bitset>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <string.h>

#define X first
#define Y second
#define MP make_pair
typedef long long ll;
using namespace std;

int mindis[101], pre[101];
bool used[101];
int eCost[101][101];

int getPathSum(int c, int p, int g){
	vector<int> edge;
	edge.push_back(eCost[p][g]);
		
	int to = p;
	for(int from = pre[to]; from != 0; from = pre[from]){
		edge.push_back(eCost[from][to]);
		to = from;
	}

	sort(edge.begin(), edge.end());

	int idx = edge.size()-1;
	for(int i = 0; i < c; i++){
		edge[idx--] /= 2;
	}
	
	int ans = 0;
	for(int i = 0; i < edge.size(); i++){
		ans += edge[i];
	}

	return ans;
}

int main(){
	int c, n, m, s, d;
	while(cin >> c >> n >> m >> s >> d){
		if(c == 0 || n == 0 || m == 0 || s == 0 || d == 0) break;

		fill(mindis, mindis+101, 1<<30);
		fill(pre, pre+101, 0);
		fill(used, used+101, false);
		for(int i = 0; i < 101; i++) fill(eCost[i], eCost[i]+101, 1<<30);


		for(int i = 0; i < m; i++){
			int a, b, cost;
			cin >> a >> b >> cost;
			eCost[a][b] = cost;
			eCost[b][a] = cost;
		}
	
		mindis[s] = 0;
		vector<int> goals;
	
		//最短経路(ダイクストラ)
		while(true){
			int v = -1;
			for(int i = 1; i <= n; i++){
				if(!used[i] && (v == -1 || mindis[v] > mindis[i])) v = i;
			}
	
			if(v == -1) break;
			used[v] = true;
	
			for(int i = 1; i <= n; i++){
				if(mindis[i] > mindis[v]+eCost[v][i]){
					if(i == d){
						//次がゴールならここでチケットを適用した総和を出して最終的な結果にする
						//それをmindisに格納しておき、今後ゴールにたどり着いたルート全てと比較
						goals.push_back(getPathSum(c, v, i));
					}else{
						mindis[i] = mindis[v]+eCost[v][i];
						pre[i] = v;
					}
				}
			}
		}
	
		int minc = 10000000;
		for(int i = 0; i < goals.size(); i++){
			if(minc > goals[i]) minc = goals[i];
		}
	
		cout << minc << endl;
	}
	return 0;
}