USACO Sweet Butter

Code

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/*
ID: wcr19961
PROG: butter
LANG: C++11
*/
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
typedef long long LL;
const int inf = 0x3f3f3f3f;
const int maxn = 810;
int a[maxn];
struct Edge {
int from, to, dist;
Edge(int u, int v, int d): from(u), to(v), dist(d) {}
};
struct Dijkstra {
int n, m;
vector<Edge> edges;
vector<int> G[maxn];
bool done[maxn];
int d[maxn];
int p[maxn];
void init(int n) {
this->n = n;
for (int i = 0; i <= n; ++i) {
G[i].clear();
}
edges.clear();
}
void AddEdge(int from, int to, int dist) {
edges.push_back(Edge(from, to, dist));
m = int(edges.size());
G[from].push_back(m - 1);
}
struct HeapNode {
int d, u;
HeapNode(int d, int u): d(d), u(u) {}
bool operator < (const HeapNode& rhs) const {
return d > rhs.d;
}
};
void dijkstra(int s) {
priority_queue<HeapNode> Q;
for (int i = 0; i < n; ++i) {
d[i] = inf;
}
d[s] = 0;
memset(done, 0, sizeof done);
Q.push(HeapNode(0, s));
while (!Q.empty()) {
HeapNode x = Q.top();
Q.pop();
int u = x.u;
if (done[u]) {
continue;
}
done[u] = true;
for (int i = 0; i < G[u].size(); ++i) {
Edge& e = edges[G[u][i]];
if (d[e.to] > d[u] + e.dist) {
d[e.to] = d[u] + e.dist;
p[e.to] = G[u][i];
Q.push(HeapNode(d[e.to], e.to));
}
}
}
}
} dij;
int main() {
freopen("butter.in", "r", stdin);
freopen("butter.out", "w", stdout);
int N, P, C;
scanf("%d%d%d", &N, &P, &C);
for (int i = 0; i < N; ++i) {
scanf("%d", &a[i]);
}
dij.init(P + 1);
for (int i = 0; i < C; ++i) {
int u, v, len;
scanf("%d%d%d", &u, &v, &len);
dij.AddEdge(u, v, len);
dij.AddEdge(v, u, len);
}
int ans = inf;
for (int i = 1; i <= P; ++i) {
dij.dijkstra(i);
int res = 0;
for (int j = 0; j < N; ++j) {
res += dij.d[a[j]];
if (res > inf) {
res = inf;
}
}
if (res < ans) {
ans = res;
}
}
printf("%d\n", ans);
return 0;
}

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