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318.cpp
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318.cpp
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#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <vector>
#include <queue>
using namespace std;
int n, m, ct = 1;
int from, to, v;
int inq[550], dis[550];
struct AA {
int y, dis;
AA(int _y, int _dis) {
y = _y;
dis = _dis;
}
};
vector<AA> V[550];
void init() {
for (int i = 0; i <= n; i++) {
V[i].clear();
}
for (int i = 0; i < 550; i++) {
dis[i] = 2147483647;
}
memset(inq, 0, sizeof(inq));
}
void spfa() {
int st = 1;
dis[st] = 0;
queue<int> Q;
Q.push(st);
while (!Q.empty()) {
int cur = Q.front(); Q.pop();
inq[cur] = 0;
for (int i = 0; i < V[cur].size(); i++) {
AA tmp = V[cur][i];
if (dis[cur] + tmp.dis < dis[tmp.y]) {
dis[tmp.y] = dis[cur]+tmp.dis;
if (!inq[tmp.y]) {
Q.push(tmp.y);
}
}
}
}
}
int main(int argc, char *argv[])
{
while (~scanf("%d%d", &n, &m)) {
if (n == 0 && m == 0) {
break;
}
init();
for (int i = 0; i < m; i++) {
scanf("%d%d%d", &from, &to, &v);
V[from].push_back(AA(to, v));
V[to].push_back(AA(from, v));
}
spfa();
double PMAX = 0, MMAX = 0;
int Pindex = 1, Min1 = 1, Min2 = 1;
for (int i = 0; i <= 500; i++) {
if (dis[i] != 2147483647) {
if (dis[i] > PMAX) {
PMAX = dis[i];
Pindex = i;
}
}
}
for (int i = 0; i <= n; i++) {
for (int j = 0; j < V[i].size(); j++) {
int mmax = (dis[i] > dis[V[i][j].y])?dis[i]:dis[V[i][j].y];
int mmin = (dis[i] > dis[V[i][j].y])?dis[V[i][j].y]:dis[i];
double tmp = (mmin + V[i][j].dis - mmax)/2.0 + mmax;
if (tmp > MMAX) {
MMAX = tmp;
Min1 = i;
Min2 = V[i][j].y;
}
}
}
printf("System #%d\n", ct++);
if (PMAX >= MMAX) {
printf("The last domino falls after %.1lf seconds, at key domino %d.\n\n", PMAX, Pindex);
} else {
if (Min1 > Min2) {
int t = Min1; Min1 = Min2; Min2 = t;
}
printf("The last domino falls after %.1lf seconds, between key dominoes %d and %d.\n\n", MMAX, Min1, Min2);
}
}
return 0;
}