이 제출은 이전 버전의 oj.uz에서 채점하였습니다. 현재는 제출 당시와는 다른 서버에서 채점을 하기 때문에, 다시 제출하면 결과가 달라질 수도 있습니다.
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int maxn = 1e5+5;
int n, m, k;
struct Edge
{
int from, to, wt;
};
vector<Edge> adj[maxn];
int d[maxn]; //min distance from black nodes
int parent[maxn]; //memset to -1
int Find(int x) {
return parent[x] < 0 ? x : parent[x] = Find(parent[x]);
}
void Union(int x, int y) {
x = Find(x);
y = Find(y);
if (x == y) return;
if (parent[x] > parent[y]) swap(x,y);
parent[x] += parent[y];
parent[y] = x;
}
vector<Edge> mst[maxn];
const int maxk = 18;
int depth[maxn];
int par[maxk][maxn];
int mn[maxk][maxn];
void root(int i, int p) {
for (Edge& e: mst[i]) {
if (e.to == p) continue;
depth[e.to] = depth[i] + 1;
par[0][e.to] = i;
mn[0][e.to] = e.wt;
for (int k = 1; k < maxk; k++) {
par[k][e.to] = par[k-1][par[k-1][e.to]];
mn[k][e.to] = min(mn[k-1][e.to],mn[k-1][par[k-1][e.to]]);
}
root(e.to,i);
}
}
int lca(int a, int b) {
if (depth[a] > depth[b]) swap(a,b);
for (int k = maxk - 1; k >= 0; k--) {
int bb = par[k][b];
if (bb != 0 && depth[bb] >= depth[a])
b = bb;
}
if (a == b) return a;
for (int k = maxk - 1; k >= 0; k--) {
int aa = par[k][a];
int bb = par[k][b];
if (aa != bb) {
a = aa;
b = bb;
}
}
return par[0][a];
}
int walk(int a, int lc) { //returns min on path a -> lc
int res = 2e9+9;
for (int k = maxk - 1; k >= 0; k--) {
int aa = par[k][a];
if (depth[aa] >= depth[lc]) {
res = min(res,mn[k][a]);
a = aa;
}
}
return res;
}
int main()
{
//ios_base::sync_with_stdio(false); cin.tie(NULL);
memset(parent,-1,sizeof parent);
cin >> n >> m;
for (int k = 0; k < maxk; k++) {
for (int i = 0; i <= n; i++) {
mn[k][i] = 2e9+9;
}
}
vector<Edge> edges;
for (int i = 0; i < m; i++) {
int a, b, w; cin >> a >> b >> w;
adj[a].push_back({a,b,w});
adj[b].push_back({b,a,w});
edges.push_back({a,b,w});
}
cin >> k;
queue<int> bad;
for (int i = 1; i <= n; i++) {
d[i] = 2e9+9;
}
for (int i = 0; i < k; i++) {
int ai; cin >> ai;
bad.push(ai);
d[ai] = 0;
}
while (!bad.empty()) {
int f = bad.front(); bad.pop();
//cout << f << ": " << d[f] << '\n';
for (Edge& e: adj[f]) {
if (d[e.to] > d[f] + e.wt) {
d[e.to] = d[f] + e.wt;
bad.push(e.to);
}
}
}
for (Edge& e: edges) {
e.wt = min(d[e.from],d[e.to]);
//printf("%d -> %d: %d\n",e.from,e.to,e.wt);
}
sort(edges.begin(),edges.end(),[](auto a, auto b) {
return a.wt > b.wt;
});
for (Edge& e: edges) {
if (Find(e.from) == Find(e.to)) {
continue;
}
else {
Union(e.from,e.to);
mst[e.from].push_back({e.from,e.to,e.wt});
mst[e.to].push_back({e.to,e.from,e.wt});
//printf("%d -> %d: %d\n",e.from,e.to,e.wt);
}
}
root(1,1);
int Q; cin >> Q;
while (Q--) {
int a, b; cin >> a >> b;
int lc = lca(a,b);
int ans = min(walk(a,lc),walk(b,lc));
assert(ans < 2e9);
//printf("lca = %d, w1 = %d, w2 = %d\n", lc,walk(a,lc),walk(b,lc));
cout << ans << '\n';
}
}
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