132 lines
3.5 KiB
C++
132 lines
3.5 KiB
C++
#include <cstdio>
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#include <cstring>
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#include <algorithm>
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using namespace std;
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const int MAXN = 100000 + 1234;
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struct EDGE
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{
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int u, v;
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} edge[MAXN * 2];
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int cnt;
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int minchild[MAXN][2];
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int mindown[MAXN];
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int fa[MAXN][20];
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int head[MAXN];
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int n;
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int depth[MAXN], maxdepth, topk;
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bool cmp(EDGE a, EDGE b)
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{
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if(a. u != b.u) return a.u < b.u;
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return a.v < b.v;
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}
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void insert(int *s, int x)
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{
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if(x < s[0])
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{
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s[1] = s[0];
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s[0] = x;
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}
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else if(x < s[1]) s[1] = x;
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}
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void dfs(int root)
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{
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minchild[root][0] = minchild[root][1] = mindown[root] = n + 1;
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for(int p = head[root]; p < cnt && edge[p].u == root; p++)
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{
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int v = edge[p].v;
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if(v == fa[root][0]) continue;
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fa[v][0] = root;
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insert(minchild[root], v);
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depth[v] = depth[root] + 1;
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dfs(v);
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mindown[root] = min(mindown[root], mindown[v]);
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}
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maxdepth = max(maxdepth, depth[root]);
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mindown[root] = min(mindown[root], minchild[root][0]);
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}
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int findfather(int x, int step)
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{
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int k = topk - 1;
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while(step > 0)
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{
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while((1 << k) > step) k--;
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x = fa[x][k];
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step -= (1 << k);
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}
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return x;
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}
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int main()
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{
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int T;
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int q, x, y;
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scanf("%d", &T);
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while(T--)
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{
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scanf("%d%d", &n, &q);
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cnt = n - 1;
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for(int i = 0; i < cnt; i++)
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{
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scanf("%d%d", &edge[i].u, &edge[i].v);
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edge[i + cnt].u = edge[i].v;
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edge[i + cnt].v = edge[i].u;
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}
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cnt = cnt + cnt;
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sort(edge, edge + cnt, cmp);
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head[1] = 0;
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for(int i = 1; i < cnt; i++)
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if(edge[i].u != edge[i-1].u) head[edge[i].u] = i;
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fa[1][0] = 0;
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depth[1] = maxdepth = 0;
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dfs(1);
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topk = 0;
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while((1 << topk) <= maxdepth) topk++;
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for(int k = 1; k < topk; k++)
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for(int i = 1; i <= n; i++)
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if(fa[i][k - 1] != 0) fa[i][k] = fa[fa[i][k-1]][k-1];
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int mindown1[2];
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mindown1[0] = mindown1[1] = n + 1;
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for(int p = head[1]; p < cnt && edge[p].u == 1; p++)
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{
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int v = edge[p].v;
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int rv = min(mindown[v], v);
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insert(mindown1, rv);
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}
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while(q--)
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{
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scanf("%d%d", &x, &y);
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int ans1 = n + 1, ans2 =n + 1;
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if(y == 1)
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{
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int z = findfather(x, depth[x] - depth[y] - 1);
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int rz = min(z, mindown[z]);
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ans1 = (z == minchild[1][0] ? minchild[1][1] : minchild[1][0]);
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ans2 = (rz == mindown1[0] ? mindown1[1] : mindown1[0]);
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}
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else
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{
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bool flag = false;
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int z;
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if(depth[y] < depth[x])
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{
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z = findfather(x, depth[x] - depth[y] - 1);
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if(fa[z][0] == y) flag = true;
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}
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if(flag)
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{
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ans1 = (z == minchild[y][0] ? min(minchild[y][1], fa[y][0]) : min(minchild[y][0], fa[y][0]));
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ans2 = 1;
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}
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else
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{
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ans1 = minchild[y][0];
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ans2 = mindown[y];
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}
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}
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if (ans1 > n) printf("no answers!\n");
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else printf("%d %d\n", ans1, ans2);
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}
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puts("");
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}
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return 0;
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}
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