C++ :

/*
	author :hzoi_ztx
	title  :传送门 
	ALG    :双向spfa 
	comment:

	[2014 10 14 test]
*/

#include <cstdio>
#include <cstring>
#include <cctype>

#define  maxn  10005
#define  maxm  50005
#define  maxk  21
#define  info  0x7f7f7f7f
//#define  size  16419000
#define  size  1000000
int ret , ch ;

/*inline int qread() {
	ret = 0 ; while (!isdigit(ch = getchar())) ;
	while (ret = ret*10+ch-'0' , isdigit(ch = getchar())) ;
	return ret ;
}*/

struct FST{
	int to , next , len ;
} e[maxm*2] ; int star[maxn] = {0} , tot_e ;

void addEdge(int u , int v , int w) {
	tot_e ++ ; e[tot_e].to = v ; e[tot_e].len = w ;
	e[tot_e].next = star[u] ; star[u] = tot_e ;
}

int n , m , K ;
int u , v , w , k , p ;
int d[maxn][maxk] ;
bool b[maxn][maxk] = {0} ;

int q1[size] , q2[size] ;
int head = 0 , rear = -1 ;
int F(int x) { return ((x%size)+size)%size ; }
 bool empty() { return head == rear+1 ; }
 int front1() { return q1[F(head)] ; }
 int front2() { return q2[F(head)] ; }
 void push_front(int x , int y ) { head -- ; q1[F(head)] = x ; q2[F(head)] = y ; }
 void push_back(int x , int y ) { rear ++ ; q1[F(rear)] = x ; q2[F(rear)] = y ; }
 void pop_front() { head ++ ; }
 void pop_back() { rear -- ; }
 int qsize() { return rear-head+1 ; }
 int front11() { return q1[F(head+1)] ; }
 int front22() { return q2[F(head+1)] ; }

void spfa() {
	d[1][0] = 0 ;
	push_back(1 , 0) ;
	while (!empty()) {
		u = front1() ; k = front2() ; pop_front() ; b[u][k] = false ;
		p = star[u] ;
		while (p) {
			v = e[p].to ; w = e[p].len ;
			if (d[u][k]+w < d[v][k]) {
				d[v][k] = d[u][k]+w ;
				if (!b[v][k]) {
					b[v][k] = true ;
					if (d[v][k] < d[front1()][front2()]
						|| (qsize()>1 && d[v][k] < d[front11()][front22()])
					) push_front(v , k) ;
					else push_back(v , k) ;
				}
			}
			if (k<K &&d[u][k]<d[v][k+1]) {
				d[v][k+1] = d[u][k] ;
				if (!b[v][k+1]) {
					b[v][k+1] = true ;
					if (d[v][k+1] < d[front1()][front2()]
						|| (qsize()>1 && d[v][k+1] < d[front11()][front22()])
					) push_front(v , k+1) ;
					else push_back(v , k+1) ;
					
				}
			}
			p = e[p].next ;
		}
	}
}

int main() {
//	#define READ
	#ifdef  READ
		freopen("door.in" ,"r",stdin ) ;
		freopen("door.out","w",stdout) ;
	#endif
	memset(d , 0x7f , sizeof (d)) ;
//	n = qread() ;
//	m = qread() ;
//	K = qread() ;
scanf("%d%d%d", &n , &m , &K ) ;
	for (int i = m ; i > 0 ; i -- ) {
//		u = qread() ;
//		v = qread() ;
//		w = qread() ;
scanf("%d%d%d", &u , &v , &w ) ;
		addEdge(u , v , w) ;
		addEdge(v , u , w) ;
	}
	
	spfa() ;
	w = 0x7f7f7f7f ;
	for (int i = 0 ; i <= K ; i ++ ) {
		if (d[n][i] < w) w = d[n][i] ;
	}
	printf("%d\n", w ) ;
	return 0 ;
}

Pascal :

const maxn=10000; maxe=50000; max=100000000; maxq=4000000;
type
         node=record
               u,v:longint;
               w:longint;
               next:longint;
         end;
		 rec=record
		     data,k:longint;
			 end;
var
graph:array[1..2*maxe] of node;
h:array[1..maxn] of longint;
t,i,j,kk,n,m,s,orz,u,v,w:longint;
mark:array[1..maxn,0..20] of boolean;
q:array[1..maxq] of rec;
d:array[1..maxn,0..20] of longint;
procedure add( u, v, w:longint);
begin
    inc(t);
    graph[t].u := u;
    graph[t].v := v;
    graph[t].w := w;
    graph[t].next := h[u];
    h[u] := t;
end;
procedure spfa;
var u,p:longint;
    head,tail,i,k:longint;
begin
  fillchar(mark,sizeof(mark),false);
  for i:=1 to n do
	for j:=0 to 20 do
	 d[i,j]:=max;
  for i:=0 to kk do
     d[1,i]:=0;
  head:=0; tail:=1;
  q[tail].data:=1; q[tail].k:=0;
  mark[1,0]:=true;
  while (head<>tail) do {队列不空并且队尾指针没有溢出}
	  begin
        inc(head); if head=maxq then head:=1;
		u:=q[head].data; k:=q[head].k;
		mark[u,k]:=false;
		p:=h[u];  {p是邻接点的位置下标}
		while p<>0 do
			begin
	           if  d[u,k]+graph[p].w<d[graph[p].v,k] then
				   begin
			           d[graph[p].v,k]:=d[u,k]+graph[p].w;
						if not mark[graph[p].v,k] then
						   begin
					         {inc(times[graph[p].v]);
		                     if times[graph[p].v]>n then begin orz:=1; exit; end;}
							 inc(tail); if tail=maxq then tail:=1;
					         q[tail].data:=graph[p].v; q[tail].k:=k;
							 mark[graph[p].v,k]:=true;
						   end;
					end;
				if (k<kk) and (d[graph[p].v,k+1]>d[u,k]) then
                    begin
               	        d[graph[p].v,k+1]:=d[u,k];
                        if not mark[graph[p].v,k+1] then
						   begin
					         {inc(times[graph[p].v]);
		                     if times[graph[p].v]>n then begin orz:=1; exit; end;}
							 inc(tail); if tail=maxq then tail:=1;
					         q[tail].data:=graph[p].v; q[tail].k:=k+1;
							 mark[graph[p].v,k+1]:=true;
						   end;
                    end;
				p:=graph[p].next;
			end;
	 end;
end;
begin
 readln(n,m,kk);
 t:=0;
 fillchar(h,sizeof(h),0);
 fillchar(graph,sizeof(graph),0);
 for j:=1 to m do  {读入边，建立邻接表}
   begin
     readln(u,v,w);
     add(u,v,w);
     add(v,u,w);
    end;
   s:=1;
   spfa;
   j:=max;
   for i:=1 to kk do
      if d[n,i]<j then j:=d[n,i];
   writeln(j);
end.