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| #include <cstdio>
#include <algorithm>
using namespace std;
const int N = 1e4 + 10, M = 2e4 + 10, inf = 1e5;
int n, m, q, d[N], p[N], f[N], w[N], rt[N];
int idx, hd[N], nxt[M], edg[M], wt[M];
int stmp, sz[N], son[N], dfn[N], top[N], rnk[N];
struct Edge
{
int u, v, w;
bool operator<(Edge &_)
{
return w > _.w;
}
} e[M];
int find(int x)
{
return x == f[x] ? x : f[x] = find(f[x]);
}
struct Node
{
int l, r;
int mn;
} tr[N << 2];
void pushup(int x)
{
tr[x].mn = min(tr[x << 1].mn, tr[x << 1 | 1].mn);
}
void build(int x, int l, int r)
{
tr[x].l = l;
tr[x].r = r;
if (l == r)
{
tr[x].mn = w[rnk[l]];
return;
}
int mid = l + r >> 1;
build(x << 1, l, mid);
build(x << 1 | 1, mid + 1, r);
pushup(x);
}
int query(int x, int l, int r)
{
if (tr[x].l >= l && tr[x].r <= r)
return tr[x].mn;
int res = inf;
int mid = tr[x].l + tr[x].r >> 1;
if (l <= mid)
res = min(res, query(x << 1, l, r));
if (r > mid)
res = min(res, query(x << 1 | 1, l, r));
return res;
}
int queryPath(int x, int y)
{
int res = inf;
while (top[x] != top[y])
{
if (d[top[x]] < d[top[y]])
swap(x, y);
res = min(res, query(1, dfn[top[x]], dfn[x]));
x = p[top[x]];
}
if (x == y)
return res;
if (d[x] > d[y])
swap(x, y);
return min(res, query(1, dfn[x] + 1, dfn[y]));
}
void dfs1(int x)
{
sz[x] = 1;
son[x] = -1;
for (int i = hd[x]; ~i; i = nxt[i])
if (!d[edg[i]])
{
d[edg[i]] = d[x] + 1;
p[edg[i]] = x;
w[edg[i]] = wt[i];
dfs1(edg[i]);
sz[x] += sz[edg[i]];
if (son[x] == -1 || sz[edg[i]] > sz[son[x]])
son[x] = edg[i];
}
}
void dfs2(int x, int t)
{
dfn[x] = ++stmp;
rnk[stmp] = x;
top[x] = t;
if (son[x] == -1)
return;
dfs2(son[x], t);
for (int i = hd[x]; ~i; i = nxt[i])
if (edg[i] != p[x] && edg[i] != son[x])
dfs2(edg[i], edg[i]);
}
void add(int a, int b, int c)
{
nxt[++idx] = hd[a];
hd[a] = idx;
edg[idx] = b;
wt[idx] = c;
}
int main()
{
scanf("%d%d", &n, &m);
for (int i = 1; i <= n; i++)
hd[i] = -1;
for (int i = 1; i <= n; i++)
f[i] = i;
for (int i = 0; i < m; i++)
scanf("%d%d%d", &e[i].u, &e[i].v, &e[i].w);
sort(e, e + m);
for (int i = 0; i < m; i++)
if (find(e[i].u) != find(e[i].v))
{
f[f[e[i].u]] = f[e[i].v];
add(e[i].u, e[i].v, e[i].w);
add(e[i].v, e[i].u, e[i].w);
}
for (int i = 1; i <= n; i++)
if (!dfn[i])
{
d[i] = 1;
dfs1(i);
dfs2(i, i);
}
build(1, 1, n);
scanf("%d", &q);
for (int x, y; q; q--)
{
scanf("%d%d", &x, &y);
if (find(x) != find(y))
puts("-1");
else
printf("%d\n", queryPath(x, y));
}
return 0;
}
|