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| int cntdfs1, dfs[MAXnd + 10], low[MAXnd + 10];
int back[MAXnd + 10], throwback[MAXnd + 10], bottom[MAXnd + 10];
int cntdcc; vector<pair<int, int>> dcc[MAXnd + 10];
int topstk, stk[MAXnd + 10];
void Tarjan(int cur) {
dfs[cur] = low[cur] = ++cntdfs1;
if (!head1[cur]) {
dcc[++cntdcc].push_back(make_pair(cur, 0));
return;
}
stk[++topstk] = cur;
for (int i = head1[cur]; i; i = nex[i]) {
if (dfs[to[i]]) {
if (low[cur] > dfs[to[i]]) {
low[cur] = dfs[to[i]];
throwback[cur] = wei[i];
}
} else {
back[to[i]] = wei[i];
Tarjan(to[i]);
low[cur] = min(low[cur], low[to[i]]);
if (low[to[i]] >= dfs[cur]) {
++cntdcc;
int x;
x = stk[topstk--];
dcc[cntdcc].push_back(make_pair(cur, throwback[x]));
dcc[cntdcc].push_back(make_pair(x, back[x]));
while (x != to[i]) {
x = stk[topstk--];
dcc[cntdcc].push_back(make_pair(x, back[x]));
}
}
}
}
bottom[cur] = cntdfs1;
}
int tresum[MAXnd + 10];
int fa[MAXnd + 10], dep[MAXnd + 10], siz[MAXnd + 10], hson[MAXnd + 10];
void Dfs1(int cur, int f, int tsum) {
fa[cur] = f;
tresum[cur] = tsum;
dep[cur] = dep[fa[cur]] + 1;
siz[cur] = 1;
int mxsonsiz = 0;
for (int i = head2[cur]; i; i = nex[i]) {
if (to[i] == fa[cur]) continue;
Dfs1(to[i], cur, tresum[cur] + wei[i]);
siz[cur] += siz[to[i]];
if (mxsonsiz < siz[to[i]]) {
mxsonsiz = siz[to[i]];
hson[cur] = to[i];
}
}
}
int cntdfs2, nddfs[MAXnd + 10], idxdfs[MAXnd + 10], top[MAXnd + 10];
void Dfs2(int cur, int tp) {
nddfs[cur] = ++cntdfs2;
idxdfs[cntdfs2] = cur;
top[cur] = tp;
if (hson[cur]) {
Dfs2(hson[cur], tp);
}
for (int i = head2[cur]; i; i = nex[i]) {
if (to[i] == fa[cur] || to[i] == hson[cur]) continue;
Dfs2(to[i], to[i]);
}
}
void Lca(int x, int y, int &lca, int &xnear, int &ynear) {
lca = xnear = ynear = 0;
while (top[x] != top[y]) {
if (dep[top[x]] > dep[top[y]]) {
xnear = top[x];
x = fa[top[x]];
} else {
ynear = top[y];
y = fa[top[y]];
}
}
if (dep[x] > dep[y]) {
lca = y;
xnear = idxdfs[nddfs[lca] + 1];
} else if (dep[x] < dep[y]) {
lca = x;
ynear = idxdfs[nddfs[lca] + 1];
} else {
lca = x;
}
}
int cirsum[MAXnd + 10];
int n, m, q;
int N;
signed main() {
read(n, m, q);
for (int i = 1, u, v, w; i <= m; ++i) {
read(u, v, w);
Insert(head1, u, v, w); Insert(head1, v, u, w);
}
for (int i = 1; i <= n; ++i) {
if (!dfs[i]) {
Tarjan(i);
}
}
N = n;
for (int i = 1, dccsiz; i <= cntdcc; ++i) {
dccsiz = dcc[i].size();
if (dccsiz == 1) {
;
} else if (dccsiz == 2) {
Insert(head2, dcc[i][0].first, dcc[i][1].first, dcc[i][0].second);
} else {
++N;
cirsum[dcc[i][dccsiz - 1].first] = dcc[i][dccsiz - 1].second;
for (int j = dccsiz - 2; j; --j) {
cirsum[dcc[i][j].first] = cirsum[dcc[i][j + 1].first] + dcc[i][j].second;
}
cirsum[N] = cirsum[dcc[i][1].first] + dcc[i][0].second;
Insert(head2, dcc[i][0].first, N, 0);
for (int j = 1; j < dccsiz; ++j) {
Insert(head2, N, dcc[i][j].first, min(cirsum[dcc[i][j].first], cirsum[N] - cirsum[dcc[i][j].first]));
}
}
}
Dfs1(1, 0, 0);
Dfs2(1, 1);
for (int i = 1, x, y, lca, xnear, ynear; i <= q; ++i) {
read(x, y);
Lca(x, y, lca, xnear, ynear);
if (lca <= n) {
printf("%d\n", tresum[x] + tresum[y] - 2 * tresum[lca]);
} else {
int tmp = abs(cirsum[xnear] - cirsum[ynear]);
printf("%d\n", tresum[x] - tresum[xnear] + tresum[y] - tresum[ynear] + min(tmp, cirsum[lca] - tmp));
}
}
return 0;
}
|
