题目大意：单元最短路径（卡$SPFA$）
题解：$dijkstra$($\underline{\hspace{0.5em}}\underline{\hspace{0.5em}}gnu\underline{\hspace{0.5em}}pb\underline{\hspace{0.5em}}ds::priority\underline{\hspace{0.5em}}queue$优化)
卡点：无
C++ Code：
#include <cstdio>
#include <ext/pb_ds/priority_queue.hpp>
#define maxn 100010
#define maxm 200010
using namespace std;
const int inf = 0x3f3f3f3f;
int n, m, S;
int dis[maxn];
int head[maxn], cnt;
struct Edge {
int to, nxt, w;
} e[maxm];
void add(int a, int b, int c) {
e[++cnt] = (Edge) {b, head[a], c}; head[a] = cnt;
}
struct cmp {
inline bool operator () (const int &a, const int &b) const {
return dis[a] > dis[b];
}
};
__gnu_pbds::priority_queue<int, cmp> q;
__gnu_pbds::priority_queue<int, cmp>::point_iterator iter[maxn];
void dijkstra(int S) {
for (int i = 1; i <= n; i++) dis[i] = inf, iter[i] = q.push(i);
dis[S] = 0;
q.modify(iter[S], S);
while (!q.empty()) {
int u = q.top(); q.pop();
for (int i = head[u]; i; i = e[i].nxt) {
int v = e[i].to;
if (dis[v] > dis[u] + e[i].w) {
dis[v] = dis[u] + e[i].w;
q.modify(iter[v], v);
}
}
}
}
int main() {
scanf("%d%d%d", &n, &m, &S);
for (int i = 0; i < m; i++) {
int a, b, c;
scanf("%d%d%d", &a, &b, &c);
add(a, b, c);
}
dijkstra(S);
for (int i = 1; i <= n; i++) {
printf("%d ", dis[i] == inf ? -1 : dis[i]);
}
puts("");
return 0;
}