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OI-codes/AcWing/853/853.cpp

35 lines
694 B
C++

#include <bits/stdc++.h>
using namespace std;
struct node {
int u, v, w;
} g[10005];
int n, m, k, dist[505], backup[505];
void bellman_ford() {
memset(dist, 0x3f, sizeof(dist));
dist[1] = 0;
for (int i = 1; i <= k; i++) {
memcpy(backup, dist, sizeof(dist));
for (int j = 1; j <= m; j++) {
dist[g[j].v] = min(dist[g[j].v], backup[g[j].u] + g[j].w);
}
}
}
int main() {
cin >> n >> m >> k;
for (int i = 1; i <= m; i++) {
cin >> g[i].u >> g[i].v >> g[i].w;
}
bellman_ford();
if (dist[n] > 0x1f1f1f1f) {
cout << "impossible" << endl;
} else {
cout << dist[n] << endl;
}
return 0;
}