Go: package main

import (
	"bufio"
	"fmt"
	"math"
	"os"
	"strconv"
	"strings"
)

var scanner = bufio.NewScanner(os.Stdin)

const INF = 0x7FFFFFFF

var pass [][]int

func main() {
	for scanner.Scan() {
		pass = make([][]int, 200)
		for i := range pass {
			pass[i] = make([]int, 200)
		}
		buf := strings.Split(scanner.Text(), " ")
		c, _ := strconv.Atoi(buf[0])
		n, _ := strconv.Atoi(buf[1])
		m, _ := strconv.Atoi(buf[2])
		s, _ := strconv.Atoi(buf[3])
		d, _ := strconv.Atoi(buf[4])
		if c == 0 && n == 0 && m == 0 && s == 0 && d == 0 {
			break
		}
		s--
		d--
		for i := 0; i < 200; i++ {
			for j := 0; j < 200; j++ {
				pass[i][j] = INF
			}
		}
		for i := 0; i < 200; i++ {
			pass[i][i] = 0
		}
		for i := 0; i < m; i++ {
			scanner.Scan()
			buf_ := strings.Split(scanner.Text(), " ")
			a, _ := strconv.Atoi(buf_[0])
			b, _ := strconv.Atoi(buf_[1])
			f, _ := strconv.Atoi(buf_[2])
			a--
			b--
			pass[a][b] = f
			pass[b][a] = f
		}
		fmt.Println(dijkstra(s, d, c, n))
	}
}

func dijkstra(s, g, c, n int) float64 {
	d := make([][]float64, 200)
	used := make([][]bool, 200)
	for i := 0; i < 200; i++ {
		d[i] = make([]float64, 20)
		used[i] = make([]bool, 20)
	}
	for i := range d {
		for j := range d[i] {
			d[i][j] = INF
		}
	}
	d[s][c] = 0
	for {
		v := -1
		w := -1
		for u := 0; u < n; u++ {
			for i := 0; i < c+1; i++ {
				if !used[u][i] && (v == -1 || d[u][i] < d[v][w]) {
					v = u
					w = i
				}
			}
		}
		if v == -1 {
			break
		}
		used[v][w] = true
		for u := 0; u < n; u++ {
			d[u][w] = math.Min(d[u][w], d[v][w]+float64(pass[v][u]))
			if w-1 >= 0 && pass[v][u] != INF {
				d[u][w-1] = math.Min(d[u][w-1], d[v][w]+(float64(pass[v][u]/2.0)))
			}
		}
	}
	ret := float64(INF)
	for i := 0; i < c+1; i++ {
		ret = math.Min(ret, d[g][i])
	}
	return ret
}

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

using namespace std;

struct Node {
    Node(int s, int t, int c) : s(s), t(t), c(c) {}

    int s, t, c;

    bool operator<(const Node &rhs) const {
        return c > rhs.c;
    }
};

int main() {
    int c, n, m, s, d;
    while (cin >> c >> n >> m >> s >> d && n) {
        --s, --d;
        vector<vector<Node> > g(n);

        for (int i = 0; i < m; i++) {
            int a, b, c;
            cin >> a >> b >> c;
            --a, --b;
            g[a].push_back(Node(b, 0, c));
            g[b].push_back(Node(a, 0, c));
            g[a].push_back(Node(b, 1, c / 2));
            g[b].push_back(Node(a, 1, c / 2));
        }
        priority_queue<Node> Q;
        Q.push(Node(s, c, 0));
        bool flg[111][11] = {};
        while (Q.size()) {
            Node q = Q.top();
            Q.pop();
            if (flg[q.s][q.t]) continue;
            if (q.s == d) {
                cout << q.c << endl;
                break;
            }
            flg[q.s][q.t] = true;
            for (auto e : g[q.s]) {
                if (q.t >= e.t) {
                    Q.push(Node(e.s, q.t - e.t, q.c + e.c));
                }
            }
        }
    }
}

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

struct town {
	int n,tn[500],m[500],a[11];
};

town to[100];

int c,n,m,s,d;

void ans() {
	int i,j,k,f;
	for (i=0;i<n;i++) for (j=0;j<=c;j++) to[i].a[j]=9999999;
	for (i=0;i<=c;i++) to[s].a[i]=0;
	while(true)  {
		f=0;
		for (i=0;i<n;i++) for (j=0;j<to[i].n;j++) {
			 for (k=0;k<=c;k++) {
			 if (to[i].a[k]+(to[i].m[j])/2<to[to[i].tn[j]].a[k+1]) {to[to[i].tn[j]].a[k+1]=to[i].a[k]+(to[i].m[j])/2; f=1;}
			 if (to[i].a[k]+to[i].m[j]<to[to[i].tn[j]].a[k]) {to[to[i].tn[j]].a[k]=to[i].a[k]+to[i].m[j]; f=1;}
		    }
	    }
	    if (f==0) break;
	}
}
int main() {
	int i,a,b,x;
	while(cin >> c >> n >> m >> s >> d && n>0) {
		s--; d--;
		for (i=0;i<n;i++) to[i].n=0;
		for (i=0;i<m;i++) {
			cin >> a >> b >> x; a--; b--;
			to[a].tn[to[a].n]=b;  to[b].tn[to[b].n]=a;
			to[a].m[to[a].n]=to[b].m[to[b].n]=x;
			to[a].n++; to[b].n++;
		}
		ans();
		cout << to[d].a[c] << endl;
		}		 
	return 0;
}

C++: #define _USE_MATH_DEFINES
#define INF 10000000
#include <iostream>
#include <sstream>
#include <cmath>
#include <algorithm>
#include <queue>
#include <stack>
#include <limits>
#include <map>
#include <string>
#include <cstring>
#include <set>
#include <deque>
#include <bitset>
#include <list>

using namespace std;

typedef long long ll;
typedef pair <int,int> P;
typedef pair <int,P > PP;

static const double eps = 1e-8;

int path[101][101];
int used[101][11];

void bfs(int s,int d,int n,int c){
	priority_queue<PP,vector<PP>,greater<PP> > que;
	que.push(PP(0,P(s,c)));
	used[s][c] = 0;

	while(!que.empty()){
		int cost = que.top().first;
		int src = que.top().second.first;
		int ticket = que.top().second.second;
		que.pop();

		for(int dst=1;dst<=n;dst++){
			if(used[dst][ticket] > cost + path[src][dst]){
				used[dst][ticket] = cost + path[src][dst];
				que.push(PP(cost + path[src][dst],P(dst,ticket)));
			}

			if(ticket > 0 && used[dst][ticket-1] > cost + path[src][dst]/2){
				used[dst][ticket-1] = cost + path[src][dst]/2;
				que.push(PP(cost + path[src][dst]/2,P(dst,ticket-1)));
			}
		}
	}
}

int main(){
	//c:number of tickets
	//n:number of towns
	//m:number of buses
	//s:source
	//d:destination
	int c,n,m,s,d;
	while(~scanf("%d %d %d %d %d",&c,&n,&m,&s,&d)){
		if(c==n && n==m && m==s && s==d && d==0) break;
		memset(path,0x3,sizeof(path));
		memset(used,0x3,sizeof(used));

		for(int i=0;i<m;i++){
			int a,b,f;
			scanf("%d %d %d",&a,&b,&f);
			path[a][b] = path[b][a] = min(path[a][b],f);
		}

		bfs(s,d,n,c);
		int res=numeric_limits<int>::max();
		for(int i=c;i>=0;i--) res = min(res,used[d][i]);
		printf("%d\n",res);
	}
}

C++: #include <bits/stdc++.h>
#define INF (1<<29)
#define all(c) (c).begin(),(c).end()
#define pb(c) push_back(c)
using namespace std;
typedef long long ll;
typedef pair<int, int> P;
typedef pair<int, P> PP;

int dis[111][111];
int c, n, m, s, d;
int next[111][111];

void dfs(int cur, int sum, int cost){
  if(next[cur][sum] < cost) return;
  next[cur][sum] = cost;
  for(int i = 0; i < n; i++){
    if(dis[cur][i] == (1<<29)) continue;
    if(sum > 0) dfs(i, sum-1, cost+(dis[cur][i]/2));
    dfs(i, sum, cost+dis[cur][i]);
  }
}

int main(){
  ios::sync_with_stdio(false);

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

    for(int i = 0; i < 111; i++){
      for(int j = 0; j < 111; j++){
        dis[i][j] = next[i][j] = (1<<29);
      }
    }

    for(int i = 0; i < m; i++){
      int a, b, f;
      cin >> a >> b >> f;
      a--; b--;
      dis[a][b] = f;
      dis[b][a] = f;
    }

    dfs(s-1,c,0);
    int ans = (1<<29);
    for(int i =0; i < c; i++){
      ans = min(ans, next[d-1][i]);
    }
    cout << ans << endl;
  }


}