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| #include<iostream>
#include<cstdio>
#include<algorithm>
#include<queue>
#include<vector>
#include<cstring>
#define ll long long
using namespace std;
const ll N=1e4,K=10,M=5e4;
ll n,m,k,S,T,u,v,w,tot,ans;
ll ver[M*2+5],nxt[M*2+5],wt[M*2+5],head[N+5],f[N+5][K+5];
bool vis[N+5][K+5];
struct node{
ll d,v,l;
bool operator > (const node& rhs) const {
return v>rhs.v;
}
}h,t;
priority_queue<node,vector<node>,greater<node> > q;
void dij() {
memset(vis,0,sizeof(vis));
memset(f,0x3f,sizeof(f));
f[S][0]=0;t.d=S;t.l=0;t.v=f[S][0];
q.push(t);
while(!q.empty()) {
h=q.top();q.pop();
if(vis[h.d][h.l]) continue;vis[h.d][h.l]=1;
for(ll i=head[h.d];i;i=nxt[i]) {
if(f[ver[i]][h.l]>f[h.d][h.l]+wt[i]) {
f[ver[i]][h.l]=f[h.d][h.l]+wt[i];
t.d=ver[i];t.l=h.l;t.v=f[ver[i]][h.l];
q.push(t);
}
if(h.l+1<=k&&f[ver[i]][h.l+1]>f[h.d][h.l]) {
f[ver[i]][h.l+1]=f[h.d][h.l];
t.d=ver[i];t.l=h.l+1;t.v=f[ver[i]][h.l+1];
q.push(t);
}
}
}
}
void add(ll u,ll v,ll w) {
ver[++tot]=v;wt[tot]=w;
nxt[tot]=head[u];head[u]=tot;
}
inline ll read() {
ll ret=0,f=1;char ch=getchar();
while(ch<'0'||ch>'9') {if(ch=='-') f=-f;ch=getchar();}
while(ch>='0'&&ch<='9') {ret=(ret<<3)+(ret<<1)+ch-'0';ch=getchar();}
return ret*f;
}
void write(ll x) {
static char buf[22];static ll len=-1;
if(x>=0) {
do{buf[++len]=x%10+48;x/=10;}while(x);
}
else {
putchar('-');
do{buf[++len]=-(x%10)+48;x/=10;}while(x);
}
while(len>=0) putchar(buf[len--]);
}
int main() {
n=read();m=read();k=read();
S=read();T=read();
for(ll i=1;i<=m;i++) {
u=read();v=read();w=read();
add(u,v,w);add(v,u,w);
}
dij();
ans=f[T][k];
for(ll i=0;i<k;i++) {
ans=min(ans,f[T][i]);
}
write(ans);
return 0;
}
|