Title link
within the first heavy cycle plus Common floyd section of code, for the three points formed by the smallest ring, there is a problem that the pit will increase due to the three variables, INF carefully too loud explosion int.
const int INF = INT_MAX/10;
const int maxn = 1e3+10;
int g[maxn][maxn], g2[maxn][maxn], n, m, minr;
void init() {
for (int i = 1; i<=n; ++i)
for (int j = 1; j<=n; ++j)
g2[i][j] = g[i][j] = INF;
minr = INF;
}
void floyd() {
for (int k = 1; k<=n; ++k) {
for (int i = 1; i<k; ++i)
for (int j = 1; j<i; ++j)
if (minr > g[i][j] + g2[j][k] + g2[k][i])
minr = g[i][j] + g2[j][k] + g2[k][i];
for (int i = 1; i<=n; ++i)
for (int j = 1; j<=n; ++j)
if (g[i][j] > g[i][k] + g[k][j])
g[i][j] = g[i][k] + g[k][j];
}
}
int main(void) {
while(~scanf("%d%d", &n, &m)) {
init();
for (int i = 0, u, v, c; i<m; ++i) {
scanf("%d%d%d", &u, &v, &c);
g2[u][v] = g2[v][u] = g[u][v] = g[v][u] = min(g[u][v], c);
}
floyd();
if (minr==INF) printf("It's impossible.\n");
else printf("%d\n", minr);
}
return 0;
}