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OI-codes/Luogu/P2136/P2136.cpp

50 lines
1.1 KiB
C++

#include <bits/stdc++.h>
using namespace std;
int n, m, dist1[1005], dist2[1005], backup[1005];
struct node {
int s, t, w;
} g[10005];
void bellman_ford1() {
memset(dist1, 0x3f, sizeof(dist1));
dist1[1] = 0;
for (int i = 1; i <= n; i++) {
memcpy(backup, dist1, sizeof(dist1));
for (int j = 1; j <= m; j++) {
dist1[g[j].t] = min(dist1[g[j].t], backup[g[j].s] + g[j].w);
}
}
}
void bellman_ford2() {
memset(dist2, 0x3f, sizeof(dist2));
dist2[n] = 0;
for (int i = 1; i <= n; i++) {
memcpy(backup, dist2, sizeof(dist2));
for (int j = 1; j <= m; j++) {
dist2[g[j].t] = min(dist2[g[j].t], backup[g[j].s] + g[j].w);
}
}
}
int main() {
cin >> n >> m;
for (int i = 1; i <= m; i++) {
cin >> g[i].s >> g[i].t >> g[i].w;
g[i].w = -g[i].w;
}
bellman_ford1();
for (int i = 1; i <= m; i++) {
if (dist1[g[i].t] > dist1[g[i].s] + g[i].w) {
cout << "Forever love" << endl;
exit(0);
}
}
bellman_ford2();
cout << min(dist1[n], dist2[1]) << endl;
return 0;
}