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1614.cpp
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1614.cpp
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#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#define MAXN 1111
#define INF 1011111111
using namespace std;
struct EDGE
{
int v, w;
EDGE(){}
EDGE(int _v, int _w) {v = _v; w = _w;}
};
vector<EDGE>g[MAXN];
int vis[MAXN];
int dis[MAXN];
int q[MAXN * 4];
int n, k, m;
int spfa(int lim)
{
memset(vis, 0, sizeof(vis));
vis[1] = 1;
for(int i = 1; i <= n; i++) dis[i] = INF;
dis[1] = 0;
int h = 0, t = 0;
q[t++] = 1;
while(h < t)
{
int u = q[h++];
vis[u] = 0;
int size = g[u].size();
for(int i = 0; i < size; i++)
{
int v = g[u][i].v;
int w = g[u][i].w;
int ad = 0;
if(w > lim) ad = 1;
if(dis[u] + ad < dis[v])
{
dis[v] = dis[u] + ad;
if(!vis[v])
{
q[t++] = v;
vis[v] = 1;
}
}
}
}
if(dis[n] <= k) return 1;
else return 0;
}
void solve()
{
freopen("input.txt","r",stdin);
freopen("output.txt","w",stdout);
scanf("%d%d%d", &n, &m, &k);
int x, y, z;
for(int i = 0; i < m; i++)
{
scanf("%d%d%d", &x, &y, &z);
g[x].push_back(EDGE(y, z));
g[y].push_back(EDGE(x, z));
}
int low = 0, high = INF, ans = INF;
while(low <= high)
{
int mid = (low + high) >> 1;
if(spfa(mid)) ans = min(ans, mid), high = mid - 1;
else low = mid + 1;
}
if(ans == INF) ans = -1;
printf("%d\n", ans);
}
int main()
{
solve();
return 0;
}